cisco switching basics
TRANSCRIPT
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1 2004 Cisco Systems, Inc. All rights reserved.
Roland Ducomble
TAC Technical Leader CCIE 3745
August 2006
Bootcamp : GTPLan-sw fundamentals
mailto:[email protected]:[email protected] -
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Agenda
Ethernet /Autonegotiation / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
SPAN RSPAN
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802.3 Ethernet- CSMA/CD
Ready totransmit
Transmit data and
sense channel
(4)
Transmit
Jam Signal
(5)
Wait according to
backoff strategy
(6)
Sense
Channel
(1)
New attempt
Channel free
for IFG (9.6us)
(2)
Channel busy
(3)
Collision detected
Wait according to a random Binary
Exponential Backoff (BEB)
algorithm, and then try again.
After 16 consecutive
collisions,give up and discard the
frame.
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Half versus Full Duplex
Half Duplex
One station transmits, other listens.
While transmitting, you do not receive, as no one else is transmitting.
If you receive data on your RX pin WHILE youre in the process oftransmitting that is considered a collision.
Full Duplex (standardized in 802.3x)Transmit and receive at the same time.
Transmit on the transmit pair, and receive on the receive pairs.
No collision detection, backoff, retry, etc
No CS, no MA, no CD. Only relationship to HD is frame format and
encoding/signaling method.
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Fast Ethernet
Uses original Ethernet MAC frame, but operates at 10times the speed of regular Ethernet.
Retains everything that original ethernet has, except theInterFrameGap. Decreased from 9.6s to 0.96s.
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Gigabit Ethernet
Comes in 2 flavors 1000Base-T and 1000Base-X
1000Base-T Ethernet
1000Base-T scrambles each byte in the MAC frame to randomize the bit sequencebefore it is encoded using Forward Error Correction method. It is using the 4 wirepair.
Each transmitted frame is encapsulated with start-of-stream and end-of-streamdelimiters.
1000Base-T supports both half-duplex and full-duplex operation. Cisco only doesfull.
1000Base-X Ethernet
Transmission coding is based on the ANSI Fibre Channel 8B/10B encodingscheme. Each 8-bit data byte is mapped into a 10-bit code-group for bit-serialtransmission
All three 1000Base-X versions support full-duplex binary transmission at 1250Mbps over two strands of optical fiber or two STP copper wire-pairs
All 1000Base-X physical layers support both half-duplex and full-duplex operation
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Auto-negotiation Overview
Auto-negotiation is used on 10/100 M port tonegotiate speed and duplex between two peers.
Standard defined by IEEE : 802.1u
See for more info :http://www.Cisco.com/warp/customer/473/3.html
http://www.iol.unh.edu/training/fether/aneg/
http://www.cisco.com/warp/customer/473/3.htmlhttp://www.iol.unh.edu/training/fether/aneg/http://www.iol.unh.edu/training/fether/aneg/http://www.cisco.com/warp/customer/473/3.html -
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Case 1 : Both partner are capable of doingauto-negotiation
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Exchanging capabilities : The LCW
The two partners exchange their capabilities through theexchange of a LCW (link Code Word) in FLP (Fast link pulse)
The LCW is a 16 bits word sent by each auto-negotiatingpartner to its peer containing its own capabilities
Exchanged in 10baseT Pulse format The FLP is also used to detect the presence of a link
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Exchanging capabilities : The LCW (cont.)
S0 to S4 tells the protocol (802.3 in most cases)
A0 to A7 : capability (100 base TX FD, )
Ack bit : set on receipt of 3 consecutive and consistentLCW from peer
RF bit : remote fault indication NP : next page bit
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Exchanging capabilities : The LCW (cont.)
This one advertise all 4 capabilities :
100Base-TX Full Duplex
100Base-TX
10Base-T Full Duplex
10Base-T
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Choosing speed and duplex
Once capabilities has been exchanged between the twopeers, both peers choose the highest common denominatoraccording the following ranking :
1.100Base-TX Full Duplex
2.100Base-T4
3.100Base-TX
4.10Base-T Full Duplex
5.10Base-T
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Using the remote fault bit
A BFLP
FLP
A and B exchange FLP for auto-negotiation and
because of a cable fault A never receive FLP from B
and as such assume a fault and set the RF bit in theFLP it sends to B
Negotiation cannot be completed
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Case 2: one of the partner do not do auto-negotiation
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Parallel detection
The Parallel Detection Function is an auto-negotiating device'smeans to establish links with non-negotiating, fixed speeddevices.
If an auto-negotiating device receives either 10BaseT or T4 LinkTest Pulses or the idle stream of a TX device, it should do oneof two things:
enable the link at the received pulse speed if it supports it
Or refuse to establish a link.
A device can never parallel detect to a full duplex link, however.Thus in parallel detection mode WE ARE ALWAYS IN HALF-DUPLEX
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Auto-negotiation summary
Config Peer 1 Config Peer 2 Result onPeer 1
Result onPeer 2
Comments
Auto Auto 100 FD 100 FD Correct nego when bothpeer are capable of 100 FD
100 FD Auto 100 FD 100 HD DUPLEX MISMATCH
100 FD 100 FD 100 FD 100 FD Correct manual config
100 HD Auto 100 HD 100 HD Link is established, butpeer 2 does not see anyauto-negotiationinformation from NIC anddefaults to half-duplex.
10 HD Auto 10 HD 10 HD Link is established, butpeer 2 will not see FLPand will default to 10 Mbpshalf-duplex.
10 FD 100 FD No link No link SPEED MISMATCH
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Auto-Negotiation
Upon initialization, each device transmits a 16-bit message (called aFast Link Pulse Burst) to its link partner, which is used to negotiate:
Speed supported by partner;
Duplex mode supported by partner;
Flow control support via MAC control pause frames; and
It also can be used to indicate a fault and specify the type of fault. The 16-bit negotiation message should be sent repeatedly until
acknowledged by partner.
An acknowledgement should be sent after 3 consecutive messagesconfirming capabilities.
Auto-negotiation signaling is independent of the signaling/encodingused for normal data.
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Detecting a duplex mismatch
Full duplex means that the collision detection mechanism isdisable and as such a FD devices will sent frame withoutlistening to see if the media is free
Symptoms of Duplex mismatch :
FCS errors
Align errors
Late collision (seen on HD side)
Runts
Excessive collision (seen on HD side)
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Summary : 10/100 auto negotiation
use if possible :
Auto to auto
Fix speed/duplex to Fix speed/duplex
Avoid :Auto to Fix speed/duplex
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Remote fault on 100baseFX
FEFI can provide same functionality on 100M fiberport (not supported on all line card though)
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Gigabit flow control
When Gigabit flow control is enable a congestedreceiver can let know the transmitter thecongestion by sending a PAUSE frame that resultof the sender to stop transmission for a while.
Defined in 802.3x
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Gigabit auto-negotiation
Auto-negotiation in 1000baseX is different than in 10/100
What does auto-negotiation at gig speed :
Duplex negotiation
Remote fault detection
Flow control negotiation
Do not include speed negotiation.
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Gigabit auto-negotiation
Exchange word in similar way as 10/100 nego
Duplex and flow control info in the negotiation word depends oncapability and config
Once capability has been exchange, we decide on link settings
Duplex : Full duplex is the priority regarding half duplex
Flow control : PAUSE frame are enable in sending and/orreceiving direction
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Gigabit negotiation issue
Some devices do not support giga negotiation or only part ofit
In case of trouble to bring link up to different type of devices,worth to try disabling link negotiation
Note : GSR in old software do not support gig negotiation.
Nego needs to be enable on both side or the link or disableon both side of the link.
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Review
What is the result of PC 10/100 NIC auto sensing toa switch port fix in 100M full Duplex ?
What is the result of connecting to 1000 base-Xdevices where one side negotiate and the other hasnegotiation disable
If Gig nego is disable on both side of a connection,what will happen is I unplug Rx Strand of fiber onone side ?
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Ethernet Frame Types (3)Generic
Name
Novell
Name
Cisco
Name
(switch)
Ethernet
Version II
(DIX)
Ethernet_IIARPA
(EII)
Type
(>1500)DA SA FCS
802.3 w/
802.2 LLC
Header
Ethernet_802.2SAP
(8023)Length
DSAP
(1)
SSAP
(1)
Control
(1)DA SA FCSData
802.3Raw(Novell Raw) Ethernet_802.3Novell_Ether
(802.3raw)
Length
FF-FF
all 1s(2 byte)
DA SA FCSData
Data
1985: Final version of the 802.3 specification was released.
Final version of 802.3 has been modified to include the 802.2
LLC header, making NetWare's proprietary format incompatible.
Two years after that
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Ethernet Frame Types (4)Generic
Name
Novell
Name
Cisco
Name
(switch)
Ethernet
Version II
(DIX)
Ethernet_IIARPA
(EII)
Type
(>1500)DA SA FCS
802.3 w/
802.2 LLC
Header
Ethernet_802.2SAP
(8023)Length
DSAP
(1)
SSAP
(1)
Control
(1)DA SA FCSData
802.3Raw
(Novell Raw)
Ethernet_802.3Novell_
Ether
(802.3raw)
Length
FF-FF
all 1s(2 byte)DA SA FCSData
Data
SNAP Ethernet_SNAPSNAP
(snap)FCSLengthDSAP
AA
(1)
SSAP
AA
(1)
Control
03
(1)DA SA Data
OUI
(3)
Type
(2)
Finally, the 802.3 SNAP format was created to address backwards
compatibility issues between Version 2 and 802.3 Ethernet.
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Hub
Rpt
What is a Collision Domain?
What is a Broadcast Domain?
How many of each do we have here?
Hub to Bridge to Switch
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Hub
Rpt
How does the addition of switches affect collision domains?
Hub to Bridge to Switch
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Hub
Rpt
2 collision domains
1 - broadcast domain
Hub to Bridge to Switch
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Floor #3
Floor #2
Floor #1
Hub
Rpt
Hub to Bridge to Switch
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Floor #3
Floor #2
Floor #1
Hub
Rpt
How many collision
domains?
How many broadcastdomains?
Hub to Bridge to Switch
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Floor #3
Floor #2
Floor #1
Hub
Rpt
6 collision
domains
3- broadcastdomains
Hub to Bridge to Switch
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Floor #3
Floor #2
Floor #1
Hub
Rpt
How many collision
domains?
How many broadcastdomains?
Hub to Bridge to Switch
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Floor #3
Floor #2
Floor #1
Hub
Rpt
8collision
domains
1- broadcastdomain
Hub to Bridge to Switch
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Four major functions:
Learning MAC addresses;
Forwarding/filtering frames;
Forwarding broadcasts; and
Loop avoidance - Spanning Tree
Bridge Functionality
Segment SegmentPort E0 Port E1
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Address Learning
Source MAC address is associated with NIC
Addresses are learned from SA field of ethernet frame.
Independent of Destination- Unicast or Broadcast
MAC Address Table
0260.8c01.1111
0260.8c01.2222
0260.8c01.3333
0260.8c01.4444
E0 E1
Port Port
A1
B2
B1
A2
0260.8c01.5555
Por
t
0260.8c01.6666
E2
C1 C2
Pre TypeDA SA FCSData
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MAC Address Table
0260.8c01.1111
0260.8c01.2222
0260.8c01.3333
0260.8c01.4444
E0 E1
Port Port
A1
B2
B1
A2
0260.8c01.5555
Por
t
0260.8c01.6666
E2
C1 C2
Pre TypeDA SA FCSData
Address Learning
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MAC Address Table
0260.8c01.1111
0260.8c01.2222
0260.8c01.3333
0260.8c01.4444
E0 E1
Port Port
A1
B2
B1
A2
0260.8c01.5555
Por
t
0260.8c01.6666
E2
C1 C2
Pre TypeDA SA FCSData
E0: 0260.8c01.1111
Address Learning
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A1 sends a frame to B2. Forwarded.
Occurs when destination is known.
0260.8c01.1111
0260.8c01.2222
0260.8c01.3333
0260.8c01.4444
E0 E1
A1
B2
B1
A2
E2
C1 C2
MAC Address Table
E0: 0260.8c01.1111
E0: 0260.8c01.2222E1: 0260.8c01.3333
E1: 0260.8c01.4444E2: 0260.8c01.5555E2: 0260.8c01.6666
0260.8c01.5555 0260.8c01.6666
Frame Forwarding
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A1 sends a frame to A2 which is filtered.
Collisions on segment A do not affect segments B orC. Thus, they are separate collision domains.
0260.8c01.1111
0260.8c01.2222
0260.8c01.3333
0260.8c01.4444
E0 E1
A1
B2
B1
A2
E2
C1 C2
MAC Address Table
E0: 0260.8c01.1111
E0: 0260.8c01.2222E1: 0260.8c01.3333
E1: 0260.8c01.4444E2: 0260.8c01.5555E2: 0260.8c01.6666
0260.8c01.5555 0260.8c01.6666
X
Frame Filtering
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A1 sends out a broadcast which is forwarded.
Thus, there is a single broadcast domain.
0260.8c01.1111
0260.8c01.2222
0260.8c01.3333
0260.8c01.4444
E0 E1
A1
B2
B1
A2
E2
C1 C2
MAC Address Table
E0: 0260.8c01.1111
E0: 0260.8c01.2222E1: 0260.8c01.3333
E1: 0260.8c01.4444E2: 0260.8c01.5555E2: 0260.8c01.6666
0260.8c01.5555 0260.8c01.6666
Handling Broadcasts
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Agenda
Ethernet / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction
VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
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Address Learning
EARL = Enhanced Address Recognition Logic
The EARL is the logic that maintains the MAC address tablejust like any learning bridge.
The table where these addresses are stored is referred to asthe CAM (content-addressable memory) because it is hashedby MAC address.
Each entry is a MAC address, port association (based onSA), and VLAN ID.
What are the elements that actually accomplish addresslearning?
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CAM Table
The EARL consults the CAM table for a MAC corresponding tothe destination address (DA) of each frame, to determine theegress port(s).
DAs that are not already known are flooded to all ports in thesame VLAN as the inbound frame.
Entries are added by the source address (SA) of the frame.
By default, entries will age out at 300 seconds.
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The Switching/Data Bus (usually called Dbus):
Catalyst 5000/5500: Dbus has a data transfer rate of1.2 Gbps.
The 5500 series has 3-1.2 Gb buses.
Catalyst 6000/6500: Dbus has a data transfer rate of 16-Gbps.
A bus access arbitration scheme is implemented on the supervisor engine, and allline modules and the supervisor have equal access to the switching bus.
The Management Bus: Carries configuration information from the NMP to each
module and statistical information from each module to the NMP, using SCP. Alsocalled MBUS or EOBC (Ethernet Out Of Band Channel).
The Results/Index Bus: Carries port-select (LTL, CBL, etc.) information from thecentral EARL to the ports. This information determines which ports forward the packetand which flush it from the buffer. It is also called RBUS.
Architecture A Couple of Quick Points
Catalyst 6K
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Catalyst 6KWhat does it LOOK like?- Chassis
Chassis
6509 65066509-NEB 6513
6503
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What does it LOOK like? - Supervisor
SupervisorSup1
Sup1A
Sup2
Sup720 (Sup-3)
Routing-Engines MSFC
MSFC2
MSFC3
Switching-EnginesCafe2
PFC
PFC2
PFC3
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What does it LOOK like? - Linecards
Linecard
2 ATM
17 WAN
15 FastEthernet / Ethernet
2 10GigEthernet
11 Special
7 GigEthernet
What does it LOOK like?
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Daughter Cards
Linecard daughter cards
What does it LOOK like?
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Daughter Cards
Linecard daughter cards
What does it LOOK like?
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Daughter Cards
Linecard daughter cards
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Agenda
Ethernet / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
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Cat OS versus IOS?? (1)
1994Cisco acquires Kalpana, a leading p rovid er ofEthernet switches worldwide.
Cisco gains the Catalyst 5000 and a whole new operatingsystem and command lineCatalyst OS.
Cisco customers must now learn two CLIs:IOS on routers and CatOS on switches
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IOS
More and more widespread for most of the newcatalyst
Allow configuring L2 feature (Catos like feature)
And L3 feature (like pure ios on routers) A port can be a L2 port or an L3 Port (on some
catalyst)
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Cat6500 Cases
Cat 6500 is composed of a supervisor (called SP orPFC) and a routing engine (called MSFC)
MSFC is daughter on supervisor (not user visibleand no separate console)
Two software option :
Hybrid : CatOS on sup and IOS on MSFC 2 config files, 2separate software
Native: Unique bundled IOS image running on both supand MSFC unique IOS file and unique config file.
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Cat OS versus IOS?? (2)
Comparing and Contrasting
IOS
Two config files (running-config
and startup-config).
Must manually save changes from
running to startup or changes
are lost.
Multiple modes of operation
(EXEC, Privileged EXEC, Global
Config, Interface Config, etc).
Designed primarily for Layer-3,
routing operations.
Ports are disabled by default. Must
issue no shut command.
Command syntax varies.
Cat OS
One config file.
Changes to config saved
automatically.
Only two modes of operation,
EXEC and Privileged EXEC.
Designed primarily for Layer-2,
switching operations.
Ports are enabled by default.
Virtually all config commands
begin with set (i.e. set vlan 99).
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IOS on Switches (1)
Catalyst 5000 is the first switch to offer integrated routing capabilitywith the RSM (Route Switch Module).
Now a single chassis had TWO operating systems:
Supervisor runs CatOS for switching functions; and
RSM runs IOS for routing functions.
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IOS on Switches (2)
This trend (CatOS and IOS BOTH on the same box) continued fora few years:
Catalyst 5000 Route Switch Feature Card (RSFC)
Catalyst 6000 Multilayer Switching Module (MSM)
Catalyst 6000 Multilayer Switching Feature Card (MSFC)
Customers become tired of shuffling back and forth between twooperating systems.
There is a big push to get rid of CatOS and make everything IOS.
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A new, specialized version of IOS, capable of doing routing AND switching, isbuilt.
Now almost ALL Cisco switches run IOS, and CatOS is virtually extinct.
With IOS on a switch, all the same IOS rules apply.
There are 2 configuration files (startup-config and running-config).
Running-config must be manually saved to startup-config using the writememory command.
There are no more set commands.
What DOES still run CatOS?
Catalyst 5000 platform (EOLno longer sold);
Catalyst 6000 when running in Hybrid; and
Catalyst 4000/4500 with Supervisor-1 or Supervisor-2.
IOS on Switches (3)
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Agenda
Ethernet / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
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Hub to Bridge to Switch
Floor #3
Floor #2
Floor #1
Hub
Rpt
8Collision
Domains
1- Broadcast
Domain
S
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Floor #3
Floor #2
Floor #1
Hub
Rpt
What if I wanted
each floor to be in
its own, unique
broadcast domain?
Hub to Bridge to Switch
H b t B id t R t
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Floor #3
Floor #2
Floor #1
A1
A2A3
A4
B1
B2B3
B4
C1C2
C3
C4
C1, C2 C3, C4
A1, A2 A3, A4
B1, B2 B3, B4
Bridge A
Bridge B
Bridge C
One way to do itseparate
each floor using a router.
Hub to Bridge to Router
H b t B id t R t
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Floor #3
Floor #2
Floor #1
A1
A2A3
A4
B1
B2B3
B4
C1C2
C3
C4
C1, C2 C3, C4
A1, A2 A3, A4
B1, B2 B3, B4
Bridge A
Bridge B
Bridge C
But whats the downside?
Hub to Bridge to Router
H b t B id t R t
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Floor #3
Floor #2
Floor #1
A1
A2A3
A4
B1
B2B3
B4
C1C2
C3
C4
C1, C2 C3, C4
A1, A2 A3, A4
B1, B2 B3, B4
Bridge A
Bridge B
Bridge C
1. Each floor needs its
own switch
2. Router interfaces areexpensive
Hub to Bridge to Router
Th S l ti VLAN !!
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The SolutionVLANs!!
VLAN = Method of micro-segmenting an L2 / L3
topology.
Each VLAN is a separate broadcast domain.
Any port on a Catalyst switch can be in any
VLAN.
Inter-VLAN communication requires a L3
routing device.
VLANs may span multiple switches.
A VLAN A P t
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Any VLAN on Any Port
Blue = VLAN10
Red = VLAN 20
Green = VLAN 30
VLAN T i
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VLAN Tagging
FCS is checked on a frame at the ingress port.
If the FCS is good, the VLAN id tag is added to the framebefore it is placed on the switching bus.
VLAN belonging to this port.
Port ID of this port.The tag is removed at the egress port(s).
VLAN C fi ti (C t OS)
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VLAN Configuration (Cat OS)
To add VLAN
set vlan
To remove VLAN
clear vlan To view configured VLANs
show vlan
VLAN C fi ti ( C t IOS )
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VLAN Configuration ( Cat IOS )
Enter vlan database
3524XL#vlan database
Must be in server mode
3524XL(vlan)#vtp server
Add vlan
3524XL(vlan)#vlan 2
Remove vlan
3524XL(vlan)#no vlan 2
Enter Global Config
4500#config t
Must be in server mode4500(config)#vtp server
Add vlan
4500(config)#vlan 2
Remove vlan
4500(config)#no vlan 2
The old way The new way
Still required on XL series switches.
VLAN C t
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VLAN Caveats
What happens if I delete a VLANand there are still
ports assigned to that VLAN?
VLAN Caveats
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VLAN Caveats
Creating VLAN 60 and assigning it to port 3/21.
VLAN Caveats
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VLAN Caveats
Verifying
VLAN Caveats
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VLAN Caveats
Now I delete the VLANwithout first moving the port toan alternate VLAN.
VLAN Caveats
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VLAN Caveats
So whats the status now of port 3/21??
Deactivated!!
Linking Different Switches
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Linking Different Switches
Building 2Building 1
I have several departments that span more than one building.
Each department has their own VLAN.How can I connect the buildings and maintain the broadcast
domains?
Linking Different Switches
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Linking Different Switches
Building 2
Building 1
Linking Different Switches
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Linking Different Switches
Building 2
Building 1
Linking Different Switches
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Linking Different Switches
Building 2
Building 1
Question: What is the design
problem with this method?
Linking Different Switches
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Linking Different Switches
Building 2
Building 1
Answer: Too many ports are used
just for switch-to-switch
connections!
Trunking to the Rescue
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Trunking to the Rescue
Trunking to the Rescue
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Trunking to the Rescue
Problem: How do you identify
which frame belongs to which
VLAN if all VLANs are carried in a
single link?
Trunking to the Rescue
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Trunking to the Rescue
Answer: Well tag each frameplaced on the trunk with the VLAN
it belongs to. Trunking
encapsulation will do this for us.
Trunking Methods
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Trunking Methods
There are two trunking protocols.
ISL = Cisco proprietary
802.1q = IEEE specification
Trunking status can be negotiated on a link.
Trunking is also supported on some routers.
Some NIC vendors support trunking.
ISL Overview
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ISL Overview
All frames are encapsulated.Adds 26 byte ISL header and 4 byte CRC to ethernet frame.
VLAN ID is carried in ISL header.
ISL is sent as a giant, MAC-layer multicast: (01-00-0C-CC-CC-
CC ether type 2004).
ISL Frame Tagging
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External TaggingFrame is encapsulated with the tag
Frame is not altered (New FCS)
TAG FCS
(e.g. ISL Header)
DA SA Data FCS
DA SA Data FCS
Type/
Length
Type/
Length
ISL Frame Tagging
IEEE 802 1q Overview
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IEEE 802.1q Overview
All frames are encapsulated except the native VLAN(covered later).
A TAG is inserted into the frame, which extendsmaximum frame size to 1522 bytes from 1518 bytes.
The FCS is recomputed for the entire frame afterthe tag is inserted.
This assumes that there is only one instance ofspanning tree.
802 1q Frame Tagging
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Internal TaggingTag is inside the frame
Frame is altered (FCS recalculated)
DA SA Data FCSType/
Length
SA Data FCSDA DataType/
LengthTAG
(802.1Q Tag)
802.1q Frame Tagging
802 1q Frame Format
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DA SA Type/Len Data FCS
DA SA Type/Len Data FCSTAG
EtherType PRI VLAN ID
Token-Ring Encapsulation Flag
4 Bytes
2 Bytes 3bits 1bit 12bits
0-7 0 - 40950-1Value = 0x8100
802.1q Frame Format
What is the Native VLAN?
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What is the Native VLAN?
VLAN trunks (either ISL or 802.1q) carry traffic from all VLANs by default.
Switches and routers need to send certain management frames to each other,
such as:
CDP
VTP
DTP
If a switch has 300 VLANs, does it really need to send 300 CDP packets everyminute (one per VLAN)? No.
So if were only going to send one CDP packet, which VLAN will send that
frame?
VLAN 1
VLAN 1 is the Native VLAN (by default)
This can be changed via configuration.Native VLAN must always match on both sides of the trunk.
ISL and dot1q Frame format
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Layer 2ISL
FCS4 Bytes
Encapsulated Frame 124.5 KbytesISL Header26 Bytes
Layer 2802.1Q/p
FCSDATATypeLen
TAG4 Bytes
SADASFDPREAM.
ISL and dot1q Frame format
TPID
0x8100
CoS
CFI
VLAN ID
0-4095
16bits 3bits1bit
12bits
ISL against dot1q
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ISL against dot1q
Cisco proprietary
Encapsulation
One spanning tree per Vlanon each trunk.
All Vlan encapsulated.
30 bytes overhead per frame
IEEE standard Internal Tag
One SPT only per dot1q trunkper standard.
Native Vlan is NOT
tagged(unless dot1q-all-taggedis configured).
4 bytes overhead only perframe
DTP Feature
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DTP Feature
Dynamic negotiation of trunkingmode :
To trunk or not ?
Trunk ISL or trunk dot1q ?
(ISL preferred)
supports on, off, auto, desirable,nonegotiate
Want to trunk?802.1q or ISL?
I am ISL -auto.
DTP
DTP
DTP
Trunking Configuration (Cat OS)
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Trunking Configuration (Cat OS)
Syntax:set trunk [on|off|desirable|auto|nonegotiate] [vlans][trunk_type](vlans = 1..1005 An example of vlans is 2-10,1005)(trunk_type =isl,dot1q,dot10,lane,negotiate)
Example:set trunk 1/1 desirable dot1q
On Trunk is manually on regardless of what the other side can/cannot do. DTPframes sent.
Off Trunk is manually turned off, regardless of possible receipt of DTP frames fromremote end of link.
Auto Trunk is in a passive state waiting for receipt of DTP frames. Will not originateDTP frames.
Desirable Port wishes to become trunk. Will source/originate DTP frames to remoteport.
Nonegotiate - Trunk is manually on regardless of what the other side can/cannot do.DTP frames NOT sent.
Trunking Configuration (Cat IOS)
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Trunking Configuration (Cat IOS)
Syntax:
Switch#config t
Switch(config)#int fa0/1
Switch(config-if)# switchport
Switch(config-if)# switchport trunk encapsulation isl
Switch(config-if)# switchport mode trunk
or
Switch(config-if)# switchport mode dynamic desirable
or
Switch(config-if)# switchport mode dynamic auto
Switch(config-if)# switchport trunk native 2
Or
dot1q
Optional to change the
Native VLAN
Trunking on the RouterConfiguration (IOS)
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Configuration (IOS)
Syntax:Router#conf t
Router(config)#int fa5/0/0.1
Router(config-subif)#encapsulation isl 1
Router(config)#int fa5/0/0.2Router(config-subif)# ip address 2.2.2.2 255.0.0.0
Router(config-subif)#encapsulation isl 2
Router(config)# int fa5/0/0.3
Router(config-subif)# ip address 3.3.3.3 255.0.0.0Router(config-subif)#encapsulation isl 3
No IP addressconfiguredassuming
no users on VLAN 1
Native VLAN
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Native VLAN
Native VLAN is the VLAN a port would be assigned toif it was not participating in a trunk
In 802.1q, frames in the native VLAN are not tagged
at all by default Native VLAN on each end of a trunk MUST match for
correct operation
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Pruning VLAN : 2 methods
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u g et ods
1. Manual Pruning (best) 2. VTP pruning (to avoid) : automatic pruning relying on VTP
message. Quiet complex and do not remove port fromspanning-tree instance just reduce size of broadcastdomain
Exception : With Spanning-Tree MST manual pruning is riskyVTP pruning might be an option
DTP and VTP
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DTP sends the VTP domain name in a DTP packet.Therefore, if you have two ends of a link belongingto a different VTP domain, the trunk will not comeup if you are using DTP. In this special case, youneed to configure the trunk mode as "on ornonegotiate, on both sides, to prevent DTP fromrunning.
DTP and spanning tree
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p g
Note that a port will only starts the SPT transitionwhen the DTP negotiation is over.
Trunking on CatOS based switch
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g
Cat4k based : 4003,4006,2948G,4912G,2980Gonly support dot1q (Hw limitation)
Cat5k based : 2901,2902,2926,5002,5000,5500,5505,5509
Support both ISL and dot1q (depends on the line card)
Use sh port capa to know capabilities of the port Cat6k based
Supports both isl and dot1q on all port
Trunking verification on CatOS
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g
Taras> (enable) sh trunk
* - indicates vtp domain mismatch
Port Mode Encapsulation Status Native vlan
-------- ----------- ------------- ------------ -----------
4/3 auto n-isl trunking 1
Port Vlans allowed on trunk
-------- --------------------------------------------------4/3 1-1005
Port Vlans allowed and active in management domain
-------- ---------------------------------------------------
4/3 1-2,101-109,151-152,500,999-1000
Port Vlans in spanning tree forwarding state and not pruned
-------- ------------------------------------------------------
4/3 1-2,101-109,151-152,500,999-1000
Taras> (enable)
Trunking on the IOS based switches
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g
Interface mode :Switchport mode trunk
Switchport encapsulation .
Sh interface [fa|gig] x/x switchport
XL family switches do not support DTP
2950 only support dot1q and DTP
3550/3750/4k sup3/sup4 and 6k native do support both isl and dot1q andthey supports DTP
Trunking verification on XL switches
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g
Brush#sh int gig 0/1 switchport
Name: Gi0/1
Switchport: Enabled
Administrative mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Disabled
Access Mode VLAN: 0 ((Inactive))
Trunking Native Mode VLAN: 1 (default)Trunking VLANs Enabled: 1-3,1002-1005
Trunking VLANs Active: 1
Pruning VLANs Enabled: 2-1001
Trunking on IOS router
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g
Do not support DTP Done per sub-interface
ISL supported for ages (11.1 in enterprise, 11.2 in IP plus)
Dot1q supported in 12.0(T)
Native vlan configured on the main interface
Dot1q bridging in 12.1(3)T
Possibility to configure native vlan on sub interface with :encapsulation dot1q x native
Sample config of a trunk in ios
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p g
interface GigabitEthernet1/2switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,10-199,222,4000
switchport mode trunk
no ip address
Sample config of a trunk in ios
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Crank#sh int gig 1/2 trunk
Port Mode Encapsulation Status Native vlan
Gi1/2 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi1/2 1,10-199,222,4000
Port Vlans allowed and active in management domainGi1/2 1,10-11,100-102,155,161,166,171-173,198-199,222,4000
Port Vlans in spanning tree forwarding state and not pruned
Gi1/2 1,10-11,100-102,155,161,166,171-173,198-199,222,4000
Trunking summary
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In case of trunk problem or connectivity problemget on both side :
Sh trunk (or sh int x/x switchport)
Sh spant x/x (or sh spanning int x/x)
Sh config
Agenda
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Ethernet / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction
VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
Port Type Basics
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Access: L2 Ports (single vlan)
Port Type Basics
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How do you configure an access L2 Port (single VLAN)?
Cat4k# conf t
Enter configuration commands, oneper line. End with CNTL/Z.
Port Type Basics
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How do you configure an access L2 Port (single VLAN)?
Cat4k# conf t
Enter configuration commands, oneper line. End with CNTL/Z.
Cat4k(config)# interface fastethernet
3/1
Port Type Basics
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How do you configure an access L2 Port (single VLAN)?
Cat4k# conf t
Enter configuration commands, oneper line. End with CNTL/Z.
Cat4k(config)# interface fastethernet
3/1
Cat4k(config-if)# switchport
Different defaults per IOS version.
Dynamic Auto
Dynamic Desirable
Port Type Basics
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How do you configure an access L2 Port (single VLAN)?
Cat4k# conf t
Enter configuration commands, one
per line. End with CNTL/Z.
Cat4k(config)# interface fastethernet
3/1
Cat4k(config-if)# switchport
Cat4k(config-if)# switchport mode
access
Forces the port to be a switchport. Will not
send, or respond to, DTP.
In VLAN 1 by default
Port Type Basics
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How do you configure an access L2 Port (single VLAN)?
Cat4k# conf t
Enter configuration commands, one per
line. End with CNTL/Z.
Cat4k(config)# interface fastethernet 3/1
Cat4k(config-if)# switchport
Cat4k(config-if)# switchport mode access
Cat4k(config-if)# switchport access vlan 2
Cat4k(config-if)# end
Cat4k#
Configuration Task
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Pause the presentation now and do the following on yourownon a piece of paper:
You are on a switch at the following prompt:
Router > Catalyst IOS Switc h
Write down the commands (using only Catalyst IOS) to:
Create VLAN 55.
Assign VLAN 55 to interface fastethernet 3/1.
Ensure fastethernet 3/1 does NOT become a trunk.
Move on to the next slide when you think you have the answer.
Configuration Task (Catalyst IOS)
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Router> enable you must first type enable
Router# configure terminal
Router (config)# vlan 55 th is creates the VLAN
Router (config-vlan)# exit
Router(config)# interface fastethernet 3/1
Router (config-if)# switchport th is ensures the port is a Layer-2 switching port
Router(config-if)# switchport mode access th is ensures that the port w i l l NOT become a trunk
Router (config-if)# switchport access vlan 55 port is now in VLAN 55
Router (config-if)# no shut
Pause this slide to review your answer.
Port Type Basics
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Access: L2 Ports (single VLAN)
Trunk: L2 ports (multiple VLANs)
Port Type Basics
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Access: L2 Ports (single VLAN)
Trunk: L2 ports (multiple VLANs)
Routed: L3 ports
Direct interface like in any router today.
int Fasteth 0/0
ip address 1.1.1.1 255.0.0.0
no shut
int Fasteth 7/1
no switchport
ip address 1.1.1.2 255.0.0.0
no shut
Port Type Basics
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Access: L2 Ports (single VLAN)
Trunk: L2 ports (multiple VLANs)
Routed: L3 ports
Direct interface as in any router today.
sub-interface support on 6500 sup720
Whats the Default?
Depends on platform. On Cat6ks with Native IOS, ports arerouted and shutdown like IOS.
CAT can have a mixture of above ports configured in one box(should we call it interfaces?).
Port Type
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Router
VLAN 1 VLAN 2 VLAN 3 VLAN N
Port 1 Port 2 Port 3 Port 4 Port M
Access
Port
in VLAN1
Trunk
Port
Access
Port
in VLAN2
Routed
Port
Routed
Port
Layer 3/SW Bridging
(in Software/Hardware)
Layer 2/VLANs
(in Hardware)
Physical Ports
SVI SVI SVI
SVIs are optional; you
can route to VLAN N, but
not to VLAN 3 in this
case
Port 5
Access
Port
in VLAN3
Port Types:L2:
- Access
- Trunk
L3:
- Routed
- VLAN
Hybrid model: Router has only logical int. Cosmos handles both logical and physical.
SVI (logical int) created with int vlan command. If underlying !=L2 then SVI down.
Bridge-groups supported but no BVIno needuse CAT.
Configuration Task
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Pause the presentation now and do the following on yourownon a piece of paper:
You are on an IOS-based switch at the following prompts:
Router > Write down the command(s) (using only Catalyst IOS) to:
Configure interface Fastethernet 5/6 as a desirable 802.1q trunk.
The switch contains NO passwords.Move on to the next slide when you think you have the answer
Configuration Task (Catalyst IOS)
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Router> enable you must first type enable
Router# configure terminal
Router(config)# interface fastethernet 5/6
Router (config-if)# switchport th is ensures the port is a Layer-2 switching port
Router(config-if)# switchport trunk encapsulation dot1q you m ust conf igure the trunkingencapsulation BEFORE you con figure the trunking mod e.
Router (config-if)# switchport mode dynamic desirable
Router (config-if)# no shut
Pause this slide to review your answer.
What is a Switched Virtual Interface(SVI)?
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PCs need default gateways (routers) to reach external networks.
Typically, if a router was used, the IP address configured on thatrouters Ethernet interface would serve as the default gateway.
Router# config t
Router(config)# interface fastethernet 0/0
Router(config-if)# ip address 1.1.1.1 255.0.0.0
With Layer-3 switches (Cat6k, 3550, 4500, etc) you place the IP addresson an SVI (Switched Virtual Interface) to have the same effect:
Cat6k# config t
Cat6k(config)# interface vlan 1
Cat6k(config-if)# ip address 1.1.1.1 255.0.0.0
Default gateway address for hosts
SVI
Default gateway address for hosts
in VLAN 1
What is an SVI? (1)
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Vlan-2 Vlan-3
2.2.2.1 /8 3.3.3.1 /8
Fa 0/1
3.3.3.2 /8
Fa 0/0
2.2.2.2 /8
VLAN 2 VLAN 3
PCs need default gateways (routers) to reachexternal networks.
Typically, if a router is used, the IP address
configured on that routers Ethernet interface
servers as the default gateway.
Router# configRouter(config)# interface fastethernet 0/0
Router(config-if)# ip address 2.2.2.2 255.0.0.0
Router(config-if)# no shut
Router(config-if)# exit
Router(config)#
Router(config)# interface fastethernet 0/1
Router(config-if)# ip address 3.3.3.2 255.0.0.0
Router(config-if)# no shut
What is an SVI? (2)
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2.2.2.1 /8 3.3.3.1 /8
MSFC
With Layer 3 switches (Cat6k, 3550, 4500,
etc) the IP address is placed on an SVI to
have the same effect:
Cat6k# config t
Cat6k(config)# interface vlan 2
Cat6k(config-if)# ip address 2.2.2.2 255.0.0.0Cat6k(config)# interface vlan 3
Cat6k(config-if)# ip address 3.3.3.2 255.0.0.0
Interface Rangea useful Command
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Interface range - up to 5 ranges at once
Cosmos(config)#interface range GigabitEthernet 1/1 2 , FastEthernet4/1 - 24
Cosmos(config-if)# switchport
Cosmos(config-if)# switchport mode access
Cosmos(config-if)# switchport access vlan 25
Cosmos(config-if)# no shut
NOTE: A space is required before and after all hyphens and commas.
Review
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What kind of interface can we have an a sup720running native ?
Switchport :
L2 Trunk
L2 accessNo switchport :
Main interface
Subinterface
SVIPortchannel either L2 trunk, L2 access, L3 main or L3subinterface !!!
Review : is it a valid config ?
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Interface gig 1/1
Switchport
Switchport trunk encaps dot1q
Switchport mode trunk
Int gig 2/1
Switchport
Ip address 1.1.1.1 255.255.255.0
Int gig 3/1
No switchport
Ip address 2.2.2.2 255.255.255.0
Can we route with that config between a frame in vlan 3 incoming ongig 1/1 towards aport 3/1 ?
Can we route with that config between a frame in vlan 3 incoming ongig 1/1 towards aport 2/1 ?
Can we route a packet incoming from 3/1 withsource ip 2.2.2.10 towards a destination in vlan 4 ?
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Interface gig 1/1
Switchport
Switchport trunk encaps dot1q
Switchport trunk allowed vlan 2,3,4
Switchport mode trunk
Int gig 2/1
Switchport
Switchport mode access
Switchport access vlan 3
Int gig 3/1
No switchport
Ip address 2.2.2.2 255.255.255.0
Int vlan 3
Ip address 3.3.3.1 255.255.255.0
Is it a valid config ?
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Int gig 1/1.1
Encapsulation dot1q 3
Ip address 3.3.3.1 255.255.255.0
Int vlan 3
Ip address 1.1.1.1 255.255.255.0
Agenda
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Ethernet / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction
VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
VLAN Trunking Protocol (VTP)
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The purpose of VTP is to ease the VLANadministration of a large number of switches.
Its primary function is to carry VLAN information toall switches within VTP domain.
VTP can also be used to make intelligent decisionsabout VLAN pruning.
VTP
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VTP is Cisco proprietary.
It is managed through layer 2 multicast packets.
It only works over established trunks (cant dothrougha router).
VTP packet only goes over vlan 1 on trunk
VTP Domains
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VTP domain is empty by default (no name configured).
A VTP domain must be configured before VLANs can be created on aswitch.
CatOS:set vtp domain {name}*case sensitive, must be exact
Catalyst IOS:
Switch# config t
Switch(config)# vtp domain {name}
*case sensit ive, must b e exact
VTP Modes (Server)
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Server
Default on all switches.
Manual adding/clearing of VLANs allowed.
Generates VTP messages upon each change.
VTP Modes (Client)
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ClientMust be manually configured.
NO manual adding/clearing of VLANs allowed.
Responds to VTP messages sent from servers.
VTP Modes (Transparent)
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TransparentMust be manually configured.
Manual adding/clearing of VLANs allowed.
Will not respond to VTP messages sent from servers.
Will not generate VTP messages of its own.
Transparently passes VTP messages between servers and clients.
VTP Configuring VTP Modes
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Define VTP mode in Catalyst OS
set vtp mode {cl ient |server | t ransparent}
Define VTP mode in Catalyst IOS
Switch# config t
Switch(config)# vtp mode {cl ient |server| t ransparent}
VTP - VLAN Trunking Protocol
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ISL
ISL
VTPServer
VTPClient
VTPTransparent
VTP
Client
HeyI have some
VLANs you should
know about!
VTP information is distributedthroughout the network
VTP - VLAN Trunking Protocol
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ISL
ISL
VTPServer
VTPClient
VTPTransparent
VTP
Client
HeyI have some
VLANs you should
know about!
Great! Now I can
add those new
VLANs and Ill also
pass them on!
VTP - VLAN Trunking Protocol
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ISL
ISL
VTPServer
VTPClient
VTPTransparent
VTP
Client
HeyI have some
VLANs you should
know about!
Great! Now I can
add those new
VLANs and Ill also
pass them on!
I could care
less. But Ill
pass them on
anyway.
VTP - VLAN Trunking Protocol
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ISL
ISL
VTPServer
VTPClient
VTPTransparent
VTP
Client
HeyI have some
VLANs you should
know about!
Great! Now I can
add those new
VLANs and Ill also
pass them on!
I could care
less. But Ill
pass them on
anyway.
Thanks! Now I
can add those
new VLANs!
VTP Configuration Revision Number
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The configuration revision number is a 32 bit number that indicates thelevel of revision for a VTP packet.
Each VTP device tracks the VTP configuration revision number assignedto it, and most of the VTP packets contain the VTP configuration revisionnumber of the sender.
This information is used to determine whether the received information
is more recent than the current version.
Each time you make a VLAN change in a VTP device, the configurationrevision is incremented by one.
If a switch receives a VTP packet with a configuration revision that ishigher than its own, stored, number, the action specified in that packet is
acted upon. If it is lower or equal, the packet is ignored.
VTPThe Big One
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An existing VTP domain isrunning well
Add a new switch
Almost all production VLANsget deleted everywhere!
A Working VTP Domain
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VLAN 2
VLAN 3
VLAN 4
VLAN 1
VTP Rev 4 VTP Rev 4
VTP Rev 4
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VLANs GonePorts Inactive!
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VTP Rev 7
VTP
VLAN 2
VLAN 3
VLAN 4
VLAN 1
VTP Rev 4 VTP Rev 4
VTP Rev 4
VTP Rev 7
VTP Rev 7
VLANs GonePorts Inactive!
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VTP Rev 7
VTP
VLAN 2
VLAN 3
VLAN 4
VLAN 1
VTP Rev 4 VTP Rev 4
VTP Rev 4
VTP Rev 7
VTP Rev 7
VLANs GonePorts Inactive!
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VTP Rev 7
VTP
VLAN 2
VLAN 3
VLAN 4
VLAN 1
VTP Rev 4 VTP Rev 4
VTP Rev 4
VTP Rev 7
VTP Rev 7
VTP Rev 7
VTP
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The revision number is incremented each time a VLAN is addedor deleted via the set vlan and clear vlan commands
Revision must be synched across entire VTP domain
VLANs not known to the server of highest revision will be
deleted
Note that a vtp client can update a vtp server.
Monitoring VTP on CatOS
Use show vtp domain early and often
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Switch> show vtp domain
Domain VTP Local
Domain Name Index Version Mode Password
----------- ------- ----- ------ -----------mydomain 1 2 server -
Vlan-count Max-vlan-storage Config Revision Notifications
---------- ---------------- --------------- -------------
15 1023 5 4
Last Updater V2 Mode Pruning PruneEligible on Vlans-------------- ------- ------- -------------------------
172.20.44.30 enabled disabled 2-1000
Use show vtp domain early and often
Monitoring VTP packet on CatOS
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Sh vtp stat : shows number of each type of VTP packetreceived with of without errors :
torq (enable) sh vtp stat
VTP statistics:
summary advts received 200
subset advts received 52
request advts received 2
summary advts transmitted 0
subset advts transmitted 0
request advts transmitted 0
No of config revision errors 0
No of config digest errors 1
Monitoring VTP on IOS switch
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Usesh vtp stat
sh vtp counters
debug sw-vlan vtp ..
VTP Pruning
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Alternative to manual pruning
Nice way to control unnecessary flooding of packetsand conserve bandwidth.
If there are no ports on the switch in a given VLAN,packets will not get flooded across the trunk to thatswitch.
STP still runs on all pruned VLANs. Manually clearingtrunks will remove STP from the trunk.
VTP Normal Operation Without Pruning(1)
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switch 1
VLAN 10
VLAN 10
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VTP Normal Operation WithoutPruning (3)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
Trunk connected between both switches.
VTP Normal Operation WithoutPruning (4)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Summary Advertisement sent by
switch 1, I have some VLANs.
Configuration Register = 4
VTP Normal Operation WithoutPruning (5)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Advertisement Request sent
by switch 2, My configuration
register is lower than yours.
Please send me your list of
VLANs.
VTP Normal Operation WithoutPruning (6)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Subset Advertisement sent
by switch 1, I have VLANs 1
and 10.
Configuration Register = 4
VTP Normal Operation WithoutPruning (7)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
Broadcast generated by PC 2
2
VTP Normal Operation WithoutPruning (8)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
Broadcast is forwarded through all ports in VLAN 10
including all VLAN trunks
Inefficient utilization of trunk bandwidththeres nobody
on switch 2 who cares about the broadcast so why send
it to switch 2?
2
VTPOperation with VTP PruningEnabled (1)
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switch 1
VLAN 10
VLAN 10
Switch 2 powered on
VTPOperation with VTP Pruning Enabled(2)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
Switch-2 powered on.
No users connected yet.
VTP Operation with VTP PruningEnabled (3)
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LAN ATTT
switch 1
swit
ch 2
VLAN 10
VLAN 10
Trunk connected between both switches.
VTP Operation with VTP PruningEnabled (4)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Summary Advertisement sent
by switch 1, I have some VLANs
Configuration Register = 4
VTP Operation with VTP Pruning Enabled (5)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Advertisement Request sent
by switch 2, My configuration
register is lower than yours.
Please send me your list of
VLANs
VTP Operation with VTP PruningEnabled (6)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Subset Advertisement sent
by switch 1, I have VLANs 1
and 10
Configuration Register = 4
VTP Operation with VTP PruningEnabled (7)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
HmmmI dont have any
access ports in VLAN 10
VTP Operation with VTP PruningEnabled (8)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Join sent by switch 2
Join contains a list of all known VLANs
Each VLAN in a VTP Join message
contains a 1-bit flood descriptor
If bit for VLAN = 1 then it means
flooding is allowed across the trunk.
If bit for VLAN = 0 then it means
flooding for this VLAN is not
allowed across the trunk.
Please dont flood any traffic to me on
VLAN 10
VTP Operation with VTP PruningEnabled (9)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
Broadcast generated by PC 2
2
VTP Operation with VTP PruningEnabled (10)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
Broadcast is forwarded all ports in VLAN 10but pruned from trunk to
switch 2.
2
X
VTP Operation with VTP PruningEnabled (11)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VLAN 10
VLAN 10
HeyI have some access
ports in VLAN 10 now !
VTP Operation with VTP PruningEnabled (12)
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switch 1
swit
ch 2
VLAN 10
VLAN 10
VTP Join sent by switch 2
Bits for VLAN 1 and VLAN 10 both
set to 1 If you need to floodtraffic to me on either VLAN 1 or
VLAN 10, thats okay.
VTP Pruning - Configuration
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set vtp pruning enableBy default, all VLANs are prune eligible. You can
override this by using the clear vtp pruneeligible{vlan num} command.
Quiz!!
f
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Name some of the reasons a company may choose to
implement VLANs on their switches.
Quiz!!
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Name some of the reasons a company may choose toimplement VLANs on their switches.
To isolate broadcasts into segmented broadcast domains.
To implement a basic form of security.
To be able to implement common QoS policies based on
distinct groupings of people or departments.
Quiz!!
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What kind of networking device is required for inter-VLAN communications?
Quiz!!
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What kind of networking device is required for inter-VLAN communications?
A router
Quiz!!
Wh t i th f VLAN t k?
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What is the purpose of a VLAN trunk?
Quiz!!
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What is the purpose of a VLAN trunk?To extend VLANs across two or more switches and conserveon the quantity of ports needed to do so.
Quiz!!
-
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How many Ethernet trunking protocols can youcurrently configure on a Catalyst switchand whichone (if any) is an IEEE standard?
Quiz!!
-
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How many Ethernet trunking protocols can youcurrently configure on a Catalyst switchand whichone (if any) is an IEEE standard?
TwoISL and 802.1Q (802.1Q is an IEEE standard)
Quiz!!
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Can you configure an ISL trunk between a CiscoCatalyst switch and a non-Cisco switch?
Quiz!!
C fi ISL k b Ci
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Can you configure an ISL trunk between a CiscoCatalyst switch and a non-Cisco switch?
NoISL is Cisco-proprietary.
Quiz!!
-
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Explain the concept of a Native VLAN as it applies toVLAN trunks.
Quiz!!
Explain the concept of a Native VLAN as it applies to
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p p pp
VLAN trunks.A Native VLAN:
Is the default VLAN for that port. In other words, the VLANthat port would revert back to if trunking failed.
Is non tag in default implementation of dot1q trunking bycisco.. However latest soft allows on each switch to configurethe tagging of native vlan.
If switches do not pay attention to Layer 3 (IP
Quiz!!
-
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If switches do not pay attention to Layer 3 (IP
addresses) and you cant place an IP address on aswitchport how can you telnet to a switch runningCaTos?
See next slide for the answer
The SC0 Interface
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You cannot place an IP address on a switchport / physical interface.
You need to place an IP address SOMEWHERE on the switch so you cantelnet to it (and ping it).
The SC0 interface is:
A logical interfacedoesnt have a physical port assigned.In VLAN 1 by defaultbut can be moved to any VLAN.
So, you can assign an IP address and subnet mask to it.
If youre familiar with routers, think of the SC0 interface as equivalent to aLoopback Interface on a router.
The SC0 InterfaceCatOS Configuration
Assigning an IP Address:Console> (enable) set interface sc0 10 1 1 1 255 255 0 0
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Console> (enable) set interface sc0 10.1.1.1 255.255.0.0
Interface sc0 IP address and netmask set.Console> (enable)
Changing the VLAN:Console> (enable) set interface sc0 5
Interface sc0 vlan set.
Console> (enable) Places the SC0 into VLAN 5
Console> (enable) show port
Port Name Status Vlan Level Duplex Speed Type
----- ------------------ ---------- ---------- ------ ------ ----- ------------
2/1 notconnect 1 normal full 1000 1000BaseSX
2/2 notconnect 1 normal full 1000 1000BaseSX
2/3 connected 1 normal a-full a-100 10/100BaseTX
2/4 connected 5 normal a-full a-100 10/100BaseTX
2/5 connected 10 normal a-full a-100 10/100BaseTX
A C
B
10.0.0.1 /8 10.1.0.2 /16
10.1.0.1 /16
2/3
2/4
2/5
Question Which PC will be able to ping the switch given the above configuration?
An Important Note
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Only switches running CatOS have an SC0interface.
SC0 does NOT exist in switches running IOS. Thereis no need for it.
Agenda
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Ethernet / Bridging
Introduction to Architecture/ Cat6k Overview
CatOS / IOS Introduction VLANS / Trunking
Some Additional IOS Caveats
VTP
Etherchannel
Why Etherchannel?
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Non-ChannelCat 6500-A Cat 6500-B
5/6
5/7
5/6
5/7X
Under normal configuration, Spanning Tree wouldblock one connection.
Blocked Link = Wasted Bandwidth;
Solution
Etherchannel
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The purpose of channeling is to aggregate ports foradditional bandwidth utilization.
Etherchannel functions as an access port or trunk port.
Etherchannel is treated as a single port by spanning tree(therefore, all ports in the channel should be in same STPstate)
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Etherchannel - Configuration
FEC/GEC bundling modes (Cat OS)
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ON: Can form a channel only with a partner also in ON mode. PAgPpackets are not sent.
AUTO: Can form a channel only with a partner in DESIRABLE mode.
AUTO does not initiate negotiation.DESIRABLE: (recommended) Can form a channel with a partner in
either AUTO or DESIRABLE modes.
OFF: Can not form a channel with any port.
FEC/GEC bundling modes (Cat OS)
Etherchannel - Configuration
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EtherChannel has to be created manually becauseCatalyst 2900XL/3500XL switches do not support PortAggregation Protocol.
If the Etherchannel is connected to a CAT OS switch,the Cat OS switch must be in the ON mode.
IOS configuration note: 2900/3500XL
Etherchannel Configuration (CAT OS)
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Syntax:Console> (enable) set port channel ?
Usage: set port channel [on|off|desirable|auto]
(example of port_list: 2/1-4 or 2/1-2 or 2/5,2/6)
Console> (enable)
URL:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd/channel.htm
Etherchannel Configuration (IOS) Configure and assign the physical ports to a port channel-group
Router (config)# interface range FastEthernet 5/6 9
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd/channel.htmhttp://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd/channel.htmhttp://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd/channel.htmhttp://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_6_3/confg_gd/channel.htm -
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no ip addressswitchportswitchport access vlan 10switchport mode accessno shutchannel-group 2 mode desirable
Layer 2 Port-Channel will dynamically be created:Router# Show runInterface Port-Channel 2
no ip addressswitchportswitchport access vlan 10switchport mode access
**Note: When configuring the individual
ports/interfaces, ensure that all
configuration matches between all ports
BEFORE configuring the channel-group
command. Also ensure that all ports are up
and functional.
**Note: Once the port-channel interface is
createdall subsequent modifications tothe Etherchannel should be configured
within this interface, NOT the physical
interfaces.
Etherchannel Show Commands
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show port channel (Cat OS)
show channel traffic (Cat OS)
show agport (CAT OS)
show channel hash ( Cat OS 6500 only)
show etherchannel (RP of Native)
Etherchannel show port channel
To display port channel status and neighbor information
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Switch-A> (enable) show port channelPort Status Channel Channel Neighbor Neighbor
mode status device port
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