chapter 1 introduction to routing and packet forwarding
DESCRIPTION
Chapter 1 Introduction to Routing and Packet Forwarding. CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College [email protected] Spring 2010. This Presentation. For detailed information see the notes section within this PowerPoint. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 1Introduction to Routing and Packet Forwarding
CIS 82 Routing Protocols and Concepts
Rick Graziani
Cabrillo College
Spring 2010
2
This Presentation
For detailed information see the notes section within this PowerPoint.
This presentation is based on the Exploration course/book, Routing Protocols and Concepts.
Notes section may contain additional details For a copy of this presentation and access to my web site for other
CCNA, CCNP, and Wireless resources please email me for a username and password. Email: [email protected] Web Site: www.cabrillo.edu/~rgraziani
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Note This chapter contains mostly introductory material. Most of not all of this information will be explained in more detail
in later chapters or later courses. The bootup process and the IOS are examined in a later
course. Do not worry or focus too much on the details for now. This will all be examined and explained in the following chapters.
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For further information This presentation is an
overview of what is covered in the curriculum/book.
For further explanation and details, please read the chapter/curriculum.
Book: Routing Protocols
and Concepts By Rick Graziani and
Allan Johnson ISBN: 1-58713-206-0 ISBN-13: 978-58713-
206-3
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Topics
Inside the Router Routers are computers Router CPU and Memory Internetwork Operating
System Router Bootup Process Router Ports and Interfaces Routers and the Network
Layer Path Determination and
Switching Function Packet Fields and Frame
Formats Best Path and Metrics Equal Cost Load Balancing Path Determination Switching Function
CLI Configuration and Addressing Implementing Basic
Addressing Schemes Basic Router Configuration
Building the Routing Table Introducing the Routing
Table Directly Connected
Networks Static Routing Dynamic Routing Routing Table Principles
Inside the Router Routers are computers Router CPU and Memory Internetwork Operating System Router Bootup Process Router Ports and Interfaces Routers and the Network Layer
7
Routers are Computers
A router is a computer: The first router (ARPANET):
IMP (Interface Message Processor) Honeywell 516 minicomputer August 30, 1969.
Leonard Kleinrock and the first IMP.
8
Router physical characteristics
9
Routers forwarding packets (packet switching): From the original source to the final destination. Selects best path
A router connects multiple networks: Interfaces on different IP networks
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Router interfaces: LAN WAN
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Routers Determine the Best Path
The router’s primary responsibility: Determining the best path Forwarding packets toward their destination
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Routers Determine the Best Path
Routing table Determines best path. Best match between destination IP address and network
address in routing table
IP Packet enters router’s Ethernet interface.
Router examines the packet’s destination IP address.
Router searches for a best match between packet’s destination IP address and network address in routing table.
Using the exit-interface in the route, the packet is forwarded to the next router or the final destination.
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Router CPU and Memory
CPU - Executes operating system instructions Random access memory (RAM)
running copy of configuration file routing table ARP cache
Read-only memory (ROM) Diagnostic software used when router is powered up. Router’s bootstrap program Scaled down version of operating system IOS
Non-volatile RAM (NVRAM) Stores startup configuration. (including IP addresses, Routing protocol)
Flash memory - Contains the operating system (Cisco IOS) Interfaces - There exist multiple physical interfaces that are used to connect
network. Examples of interface types: Ethernet / fast Ethernet interfaces Serial interfaces Management interfaces
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Cisco IOS - Internetwork Operating System
Many different IOS images. An IOS image is a file that contains the entire IOS for that router.
IOS features Example IPv6 or a routing protocol such as Intermediate
System–to–Intermediate System (IS-IS).
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Router Bootup Process (more in later course)
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Bootup Process
running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
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running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
Where is the permanent configuration file stored used during boot-up? NVRAM (B)
Where is the diagnostics software stored executed by hardware modules? ROM (D)
Where is the backup (partial) copy of the IOS stored? ROM (D)
Where is IOS permanently stored before it is copied into RAM? FLASH (C)
Where are all changes to the configuration immediately stored? RAM (A)
A B C D
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running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
?
?
?
?
?
?
?
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running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
startup-config
IOS
Bootup program
ios (partial)
running-config
IOS (running)
A B C D
B A D
C D A
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1. ROM 1. POST 2. Bootstrap code executed 3. Check Configuration Register value (NVRAM) 0 = ROM Monitor mode 1 = ROM IOS 2 - 15 = startup-config in NVRAM
2. Check for IOS boot system commands in startup-config file (NVRAM) If boot system commands in startup-config a. Run boot system commands in order they appear in startup-config to locate the IOS b If boot system commands fail, use default fallback sequence to locate the IOS (Flash, TFTP,
ROM)
3. Locate and load IOS, Default fallback sequence: No IOS boot system commands in startup-config a. Flash (sequential) b. TFTP server (netboot) - The router uses the configuration register value to form a filename from
which to boot a default system image stored on a network server. c. ROM (partial IOS) or keep retrying TFTP depending upon router model - If no IOS located, get partial IOS version from ROM
4. Locate and load startup-config configuration a. If startup-config found, copy to running-config b. If startup-config not found, prompt for setup-mode c. If setup-mode bypassed, create a “skeleton” default running-config (no startup-config)
Router Boot Process – Details (later)
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Verify the router boot-up process show version command is used to view information about the
router during the bootup process (later).
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Ports and Interfaces
Port - management ports used for administrative access Interface - capable of sending and receiving user traffic. Note: However, these terms are often used interchangeably.
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Management Ports
Console port Terminal PC running terminal emulator software
No need for network access Used for initial configuration
Auxiliary (AUX) port Not all routers have auxiliary ports.
At times, can be used similarly to a console port Can also be used to attach a modem.
Note: Auxiliary ports will not be used in this curriculum.
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Router Interfaces
Interfaces - Receive and forward packets. Various types of networks Different types of media and connectors. Different types of interfaces.
Fast Ethernet interfaces - LANs Serial interfaces - WAN connections including T1, DSL, and ISDN
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Router Interfaces
Router Interface: Different network IP address and subnet mask of that network
Cisco IOS will not allow two active interfaces on the same router to belong to the same network.
FastEthernet 0/0MAC: 0c00-3a44-190a192.168.1.1/24
FastEthernet 0/0MAC: 0c00-41cc-ae1210.1.0.1/16
Serial 0/0172.16.1.1/24
Serial 0/1172.16.1.2/24
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LAN Interfaces
Ethernet and Fast Ethernet interfaces Connects the router to the LAN
Layer 2 MAC address Participates in the Ethernet
Address Resolution Protocol (ARP): Maintains ARP cache for that interface Sends ARP requests when needed Responds with ARP replies when required
Typically an RJ-45 jack (UTP). Router to switch: straight-through cable Router to router: crossover cable
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WAN Interfaces
Point-to-Point, ISDN, and Frame Relay interfaces Connects routers to external networks. The Layer 2 encapsulation can be different types including:
PPP Frame Relay HDLC (High-Level Data Link Control).
Note: MAC addresses are used only on Ethernet interfaces and are not on WAN interfaces.
Layer 2 WAN encapsulation types and addresses are covered in a later course.
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Routers at the Network Layer
Layer 3 device because its primary forwarding decision is based on the information in the Layer 3 IP packet (destination IP address).
This is known as routing.
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Routers Operate at Layers 1, 2, and 3
Path Determination and Switching Functions
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Ethernet Frame
Layer 2 addresses: Addressing PC/Router-to-PC/Router within a network
Layer 3 addresses: Original source layer 3 address (IP) to final destination layer 3
address (IP) Does not change (unless NAT is used)
IPv4 (Internet Protocol)
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Best Path
Router’s determine best-path to a network: Depends on the routing protocol A protocol used to between routers to determine “best path”
Routing protocols use their own rules and metrics. A metric:
Quantitative value used to measure the distance to a given route. Best path:
Path with the lowest metric.
Which is path is my “best path”?
?
RIP’s metric is hop count
OSPF’s metric is bandwidth
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What happens if a routing table has two or more paths with the same metric to the same destination network? (equal-cost metric)
Router will perform equal-cost load balancing.
Equal Cost Load Balancing
To reach the 192.168.1.0/24 network it is 2 hops via R2 and 2 hops via R4.
192.168.1.0/24
?
?
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Equal-Cost Paths Versus Unequal-Cost Paths
T1
T3
Can a router use multiple paths if the paths (cost, metric) to reach the destination network are not equal?
EIGRP routing protocol which supports unequal cost load balancing
192.168.1.0/24
?
?
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Packet Forwarding
Packet forwarding involves two functions:
1. Path determination function
2. Switching function
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Path Determination
Path determination function is the process of how the router determines which path to use when forwarding a packet. Router searches its routing table for match with packet’s destination
IP address. One of three path determinations results from this search:
Directly connected network Remote network No route determined
Directly connected network
Router receives packet.
Destination IP address matches a network on one of its directly connected networks.
Packet is forwarded out that network.
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Path Determination
Remote network
Router receives packet.
Destination IP address matches a remote network which can only be reached via another router.
Packet is forwarded out that network to the next-hop router.
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Path Determination Router receives packet.
Destination IP address does NOT match any network in the router’s routing table.
Packet is dropped.
No route determined
Does this mean the network does not exist?
No, only that the router does not know about that network. (later)
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Packet Forwarding: Switching Function
Switching function is the process used by a router to: Accept a packet on one interface and Forward it out another interface
Encapsulate the packet in the appropriate data-link frame type for the outgoing data link.
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What does a router do with a packet received from one network and destined for another network?
1. Decapsulates the Layer 3 packet by removing the Layer 2 frame header and trailer2. Examines the destination IP address of the IP packet to find the best path in the
routing table3. Encapsulates the Layer 3 packet into a new Layer 2 frame and forwards the frame
out the exit interface
Dest. MAC 0B-31
Source MAC 00-20
Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
Dest. MAC 00-10
Source MAC 0A-10
Type 800
Trailer
Path Forwarding
192.168.1.10
192.168.4.10
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Remember: Encapsulation
Now, let’s do an example…
Destination IP Address
Source IP Address
Other IP fields
Data
Destination Address
Source Address
Type Data Trailer
Layer 3 IP Packet
Layer 2 Data Link Frame
Current Data Link Address of Host or Router’s exit interface
Next hop Data Link Address of Host or Router’s interface
These change from host to router, router to router, and router to host.
These addresses do not change!
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This is just a summary. The details will be shown next! Now for the details…
Dest. MAC 00-10
Source MAC 0A-10
Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
Dest. MAC 0B-31
Source MAC 00-20
Type 800
TrailerDest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
DataDest. Add FF-FF
Source Add Type 800
Trailer
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Dest. MAC 00-10
Source MAC 0A-10
Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
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Dest. MAC 0B-31
Source MAC 00-20
Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
RTA Routing TableNetwork Hops Next-hop-ip Exit-interface192.168.1.0/24 0 Dir.Conn. e0192.168.2.0/24 0 Dir.Conn e1192.168.3.0/24 1 192.168.2.2 e1192.168.4.0/24 2 192.168.2.2 e1
RTA ARP CacheIP Address MAC Address192.168.2.2 0B-31
Dest. MAC 00-10
Source MAC 0A-10
Type 800
Trailer
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Dest. Add FF-FF
Source Add Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
RTB Routing TableNetwork Hops Next-hop-ip Exit-interface192.168.1.0/24 1 192.168.2.1 e0192.168.2.0/24 0 Dir.Conn e0192.168.3.0/24 0 Dir.Conn s0192.168.4.0/24 1 192.168.3.2 s0
Dest. MAC 0B-31
Source MAC 00-20
Type 800
Trailer
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Dest. MAC 0B-20
Source MAC 0C-22
Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
RTC ARP CacheIP Address MAC Address192.168.4.10 0B-20
RTC Routing TableNetwork Hops Next-hop-ip Exit-interface192.168.1.0/24 2 192.168.3.1 s0192.168.2.0/24 1 192.168.3.1 s0192.168.3.0/24 0 Dir.Conn s0192.168.4.0/24 0 Dir.Conn e0
Dest. Add FF-FF
Source Add Type 800
Trailer
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Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
Dest. MAC 0B-20
Source MAC 0C-22
Type 800
Trailer
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The summary once again!
Dest. MAC 00-10
Source MAC 0A-10
Type 800
Trailer
Layer 2 Data Link Frame
Dest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
Data
Layer 3 IP Packet
Dest. MAC 0B-31
Source MAC 00-20
Type 800
TrailerDest. IP 192.168.4.10
Source IP 192.168.1.10
IP fields
DataDest. Add FF-FF
Source Add Type 800
Trailer
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CLI Configuration and Addressing
Before we begin: Download: Packet Tracer File:
http://netacad.cabrillo.edu/curriculum/graziani/cis82/labs-e2/e2-1-5-2.pkt
Download and Install Packet Tracer you have not done so already: http://www.cabrillo.edu/~rgraziani/
courses/cis81.html Download Lab:
http://netacad.cabrillo.edu/curriculum/graziani/cis82/labs-e2/en_ERouting_ILM_v4050.pdf
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Hands-on LabsNetworking Lab: Room 2504 and CTC NetLab
Packet Tracer (Not for homework)Check-out Pods
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Establishing a HyperTerminal session (next week)
Take the following steps to connect a terminal to the console port on the router: Connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 or
RJ-45 to DB-25 adapter. Configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits,
no parity, 1 stop bit, and no flow control.
Rollover cable
Console port
Com1 or Com2 serial port
Terminal or a PC with terminal emulation software
Router
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Establishing a Terminal session
Important: A console connection is not the same as a network connection!
=
Tera Term HyperTerminal (comes with Windows) Putty
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Terminal ConnectionNo network connection needed Console Port
When do you need to use a console connection to the router?
What software do you need?
What cable and ports do you use?
When there is not a network connection to the router (can’t use telnet).
Tera Term, HyperTerminal, Putty, etc.
PC: Serial port & Router: Console PortRollover or Console Cable
Serial
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C:\> telnet
C:\> ping
Ethernet ConnectionNetwork connection needed
When can you use a network connection to the router?
What software/command do you need?
What cable and ports do you use?
When should you not use a network connection to configure the router?
When there is a network connection to the router (telnet).
TCP/IP, Terminal prompt (DOS), Tera Term, etc.
PC & Router: Ethernet NICEthernet straight-through cable
When the change may disconnect the telnet connection.
NIC
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Terminal ConnectionNo network connection needed Console Port
C:\> telnet
C:\> ping
Ethernet ConnectionNetwork connection needed
Serial
NIC
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Serial Connectors
2500 have the “older,” larger serial interfaces Later Cisco routers use the smart serial interfaces which allows
more data to be forwarded across fewer cable pins.
Smart Serial
“Older” Serial
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Serial Cables
Router is typically a DTE device. The DTE cable is connected to the serial interface
on the router to a CSU/DSU device (DCE).
DCE Side DTE Side
DCE Cable DTE Cable
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WAN Interface Configuration
R1(config)# interface Serial0/0
R1(config-if)# ip address 192.168.2.1 255.255.255.0
R1(config-if)# description Link to R2
R1(config-if)# clock rate 64000 DCE Only
R1(config-if)# no shutdown
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Let’s do Lab 1.5.2 using Packet Tracer
Download: Packet Tracer File: http://netacad.cabrillo.edu/curriculum/graziani/cis82/labs-e2/e2-1-5-2.pkt
Download Lab: http://netacad.cabrillo.edu/curriculum/graziani/cis82/labs-e2/E2_Lab_1_5_2_cabrillo.doc
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Your Interfaces may differ
R1# show ip interface briefInterface IP-Address OK? Method Status
Protocol
FastEthernet0/0 192.168.1.1 YES manual up up
FastEthernet0/1 192.168.1.2 YES manual up up
Serial0/0 192.168.2.1 YES manual up up
Serial0/1 unassigned YES manual up up
FastEthernet 0 = FastEthernet 0/0
FastEthernet 1 = FastEthernet 0/1 = FastEthernet 1/0
Serial 0 = Serial 0/0 = Serial 0/0/0
Serial 1 = Serial 0/1 = Serial 0/0/1
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Command Overview (partial list from lab)Router> user mode
Router> enable
Router# privilege mode
Router# configure terminal
Router(config)# exit
Router# config t
Router(config)# hostname name
Router(config)# enable secret password privilege passwordRouter(config)# line console 0 console passwordRouter(config-line)# password passwordRouter(config-line)# loginRouter(config)# line vty 0 4 telnet passwordRouter(config-line)# password passwordRouter(config-line)# login
Router(config)# banner motd # message # banner
Router(config)# interface type number configure interface
Router(config-if)# ip address address mask
Router(config-if)# description description
Router(config-if)# no shutdown
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Other Commands
Router# copy running-config startup-config
Router# show running-config
Router# show ip route
Router# show ip interface brief
Router# show interfaces
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Different Modes
IOS commands must be entered in the correct mode.
Router# hostname R1
^
% Invalid input detected at '^' marker.
Router# configure terminal
Router(config)# hostname R1
R1(config)#
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Serial Connectors
2500 have the “older,” larger serial interfaces Later Cisco routers use the smart serial interfaces which allows
more data to be forwarded across fewer cable pins.
Smart Serial
“Older” Serial
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Serial Connectors
Router is typically a DTE device. The DTE cable is connected to the serial interface on the router to a
CSU/DSU device (DCE).
DTE Cable
DCE Cable
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WAN Interface Configuration
R1(config)# interface Serial0/0
R1(config-if)# ip address 192.168.2.1 255.255.255.0
R1(config-if)# description Link to R2
R1(config-if)# clock rate 64000 DCE Only
R1(config-if)# no shutdown
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Unsolicited Messages from IOS
The IOS often sends unsolicited messages Does not affect the command Can cause you to lose your place when typing.
R1(config)# interface fastethernet0/0
R1(config-if)# ip address 172.16.3.1 255.255.255.0
R1(config-if)# no shutdown
R1(config-if)# descri
*Mar 1 01:16:08.212: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
*Mar 1 01:16:09.214: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/0, changed state to upption
R1(config-if)#
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Unsolicited Messages from IOS
To keep the unsolicited output separate from your input, enter line configuration mode for the console port and add the logging synchronous
R1(config)# line console 0
R1(config-line)# logging synchronous
R1(config-if)# descri
*Mar 1 01:28:04.242: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up
*Mar 1 01:28:05.243: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/0, changed state to up
R1(config-if)# description
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LAN Interface Configuration
R1(config)# interface FastEthernet0/0
R1(config-if)# ip address 192.168.1.1 255.255.255.0
R1(config-if)# description R1 LAN
R1(config-if)# no shutdown
Fa0/1
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Each Interface Belongs to a Different Network
R1(config)# interface FastEthernet0/1R1(config-if)# ip address 192.168.1.2 255.255.255.0192.168.1.0 overlaps with FastEthernet0/0R1(config-if)# no shutdown192.168.1.0 overlaps with FastEthernet0/0FastEthernet0/1: incorrect IP address assignment
Fa0/1192.168.1.1/24
192.168.1.2/24
Same Network!
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Each Interface Belongs to a Different Network
R1# show ip interface briefInterface IP-Address OK? Method Status
ProtocolFastEthernet0/0 192.168.1.1 YES manual up upSerial0/0 192.168.2.1 YES manual up upFastEthernet0/1 192.168.1.2 YES manual administratively down downSerial0/1 unassigned YES unset administratively down down
Fa0/1
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Verifying InterfacesR1# show interfaces<some interfaces not shown>FastEthernet0/0 is up, line protocol is up (connected) Hardware is Lance, address is 0007.eca7.1511 (bia 00e0.f7e4.e47e) Description: R1 LAN Internet address is 192.168.1.1/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set ARP type: ARPA, ARP Timeout 04:00:00, Last input 00:00:08, output 00:00:05, output hang never Last clearing of “show interface” counters never Queueing strategy: fifo Output queue :0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles<output omitted>Serial0/0 is up, line protocol is up (connected) Hardware is HD64570 Description: Link to R2 Internet address is 192.168.2.1/24 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec) Last input never, output never, output hang never<output omitted>
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Verify Router ConfigurationR1# show running-config!version 12.3!hostname R1!interface FastEthernet0/0description R1 LANip address 192.168.1.1 255.255.255.0!interface Serial0/0description Link to R2ip address 192.168.2.1 255.255.255.0clock rate 64000!banner motd ^C******************************************WARNING!! Unauthorized Access Prohibited!!******************************************^C!line con 0password ciscologinline vty 0 4password ciscologin!end
Note: shutdown is the default. no shutdown does not show in the configuration.
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Save ConfigurationR1# copy running-config startup-configR1# show startup-configUsing 728 bytes!version 12.3!hostname R1!interface FastEthernet0/0description R1 LANip address 192.168.1.1 255.255.255.0!interface Serial0/0description Link to R2ip address 192.168.2.1 255.255.255.0clock rate 64000!banner motd ^C******************************************WARNING!! Unauthorized Access Prohibited!!******************************************^Cline con 0password ciscologinline vty 0 4password ciscologin!end
Building the Routing Table
Introducing the Routing Table Directly Connected Networks
76
Show Routing TableR1# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area* - candidate default, U - per-user static route, o - ODRP - periodic downloaded static route
Gateway of last resort is not set
C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, Serial0/0
77
Introducing the Routing Table
Routing table is a data file in RAM that is used to store route information about: Directly connected networks Remote networks
R1# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area* - candidate default, U - per-user static route, o - ODRP - periodic downloaded static route
Gateway of last resort is not set
C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, Serial0/0
78
Introducing the Routing Table
Directly connected interfaces contain the exit interface (more later)
R1# show ip route
<output omitted>
C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, Serial0/0
Exit Interfaces
79
Introducing the Routing Table
directly connected network is a network that is directly attached to one of the router interfaces.
When a router’s interface is configured with an IP address and subnet mask, the interface becomes a host on that attached network.
Active directly connected networks are added to the routing table.
R1# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<output omitted>
C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, Serial0/0
Directly Connected Networks
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Introducing the Routing Table
A remote network is a network that is not directly connected to the router.
A remote network is a network that can only be reached by sending the packet to another router.
Remote networks are added to the routing table using: (later) Dynamic routing protocol Static routes
R1# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<output omitted>
C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, Serial0/0
Remote Network
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Using NetLab
82
NetLabBasic Router Pod
Chapter 1Introduction to Routing and Packet Forwarding
CIS 82 Routing Protocols and Concepts
Rick Graziani
Cabrillo College