chapter7ccna
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Sybex CCNA 640-802Chapter 7: EIGRP and OSPF
Instructor & Todd Lammle
Chapter 7 Objectives
• Enhanced IGRP– EIGRP tables– Configuring EIGRP– Verifying EIGRP
• Open Shortest Path First– Configuring OSPF– Verifying OSPF– Configuring OSPF with wildcards
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What Is Enhanced IGRP (EIGRP)?
• Enhanced IGRP supports:– Rapid convergence– Reduced bandwidth usage– Multiple network-layer support– Uses Diffused Update Algorithm (DUAL) to select loop-free
routes and enable fast convergence– Up to six unequal paths to a remote network (4 by default)
EnhancedIGRP
IPX RoutingProtocols
AppleTalk Routing Protocol
IP RoutingProtocols
IPX RoutingProtocols
AppleTalk Routing Protocol
IP RoutingProtocols
Comparing EIGRP and IGRP
– Similar metric– Same load balancing– Improved convergence time– Reduced network overhead– Maximum hop count of 255 (100
default)– EIGRP can differentiate
between internal and external routes
EIGRP for IP
• No updates. Route updates sent only when a change occurs – multicast on 224.0.0.10
• Hello messages sent to neighbors every 5 seconds (60 seconds in most WANs)
Enhanced IGRP
EIGRP EIGRP
hello
EIGRP Terminology
Neighbor Table—IPNext Hop Interface Router
Topology Table—IPDestination 1 SuccessorDestination 1 Feasible Successor
Routing Table—IPDestination 1 Successor
Note: A feasible successor is a backup route and stored in the Topology table
EIGRP Tables
• The neighbor table and topology table are held in ram and are maintained through the use of hello and update packets.
Enhanced IGRP
EIGRP EIGRP
hello
To see all feasible successor routes known to a router, use the show ip eigrp topology command
Successor routes
• Successor route is used by EIGRP to forward traffic to a destination
• A successor routes may be backed up by a feasible successor route
• Successor routes are stored in both the topology table and the routing table
Routing Table—IPDestination 1 Successor
Topology Table—IPDestination 1 SuccessorDestination 1 Feasible Successor
Choosing Routes
• EIGRP uses a composite metric to pick the best path: bandwidth and delay of the line
• EIGRP can load balance across six unequal cost paths to a remote network (4 by default)
IPX
19.2
T1
T1 T1
IPX
AppleTalk
IP
AppleTalk
IPA B
DC
Configuring EIGRP for IP
172.16.10.010.110.1.0192.168.0.0
TokenRing
AS=10
Router(config)#router eigrp 10Router(config-router)#network 10.0.0.0Router(config-router)#network 172.16.0.0
192.168.0.0
A C
B
Enable EIGRP
Assign networks
If you use the same AS number for EIGRP as IGRP, EIGRP will automatically redistribute IGRP into EIGRP
Redistribution
Redistribution is translating one type of routing protocol into another.
Router D
Router B
Router A
Router C
EIGRP IGRP
IGRP and EIGRP translate automatically, as long as they are both using the same AS number
Route Path
Assuming all default parameters, which route will RIP (v1 and v2) take, and which route will EIGRP take?
T1 T1
100BaseT
100BaseT
10BaseT
56K
Verifying Enhanced IGRP Operation
show ip protocolsRouter#
show ip route eigrp Router#
show ip eigrp traffic Router#
show ip eigrp neighbors Router#
show ip eigrp topology Router#
• Displays the neighbors discovered by IP Enhanced IGRP
• Displays the IP Enhanced IGRP topology table
• Displays current Enhanced IGRP entries in the routing table
• Displays the parameters and current state of the active routing protocol process
• Displays the number of IP Enhanced IGRP packets sent and received
Show IP Route
-D is for “Dual”
-[90/2172] is the administrative distance and cost of the route. The cost of the route is a composite metric comprised from the bandwidth and delay of the line
P1R1#sh ip route[output cut]Gateway of last resort is not setD 192.168.30.0/24 [90/2172] via 192.168.20.2,00:04:36, Serial0/0C 192.168.10.0/24 is directly connected, FastEthernet0/0D 192.168.40.0/24 [90/2681] via 192.168.20.2,00:04:36, Serial0/0C 192.168.20.0/24 is directly connected, Serial0/0D 192.168.50.0/24 [90/2707] via 192.168.20.2,00:04:35, Serial0/0P1R1#
•Open standard•Shortest path first (SPF) algorithm•Link-state routing protocol (vs. distance vector)•Can be used to route between AS’s
Introducing OSPF
OSPF Hierarchical Routing
• Consists of areas and autonomous systems• Minimizes routing update traffic• Supports VLSM• Unlimited hop count
Link State Vs. Distance Vector
Link State:• Provides common view of entire topology• Calculates shortest path• Utilizes event-triggered updates• Can be used to route between AS’s
Distance Vector:•Exchanges routing tables with neighbors•Utilizes frequent periodic updates
Types of OSPF Routers
InternalRouters
Area 1 Area 2
ASBR andBackbone Router
Backbone/InternalRouters
ABR and BackboneRouter
Backbone Area 0
ABR and BackboneRouter
InternalRouters
•External AS
Router(config-router)#network address mask area area-id
Assigns networks to a specific OSPF area
Router(config)#router ospf process-id
Defines OSPF as the IP routing protocolNote: The process ID is locally significant and is needed to identify a unique instance of an OSPF database
Configuring Single Area OSPF
OSPF Example
hostname R3
router ospf 10 network 10.1.2.3 0.0.0.0 area 0network 10.1.3.1 0.0.0.0 area 0
hostname R2
router ospf 20network 10.0.0.0 0.255.255.255 area 0
hostname R1
router ospf 30network 10.1.0.0 0.0.255.255 area 0network 10.5.5.1 0.0.0.0 area 0
R3
R2R1
10.1.2.0
10.1.1.0
10.5.5.0
Area 010.1.3.0
Router#show ip ospf interface
Verifying the OSPF Configuration
Displays area-ID and adjacency information
Router#show ip protocols
Verifies that OSPF is configured
Router#show ip route
Displays all the routes learned by the router
Router#show ip ospf neighbor
Displays OSPF-neighbor information on a per-interface basis
OSFP Neighbors• OSPF uses hello packets to create
adjacencies and maintain connectivity with neighbor routers
• OSPF uses the multicast address 224.0.0.5
Hello?224.0.0.5
•Hello packets provides dynamic neighbor discovery•Hello Packets maintains neighbor relationships•Hello packets and LSA’s from other routers help build and maintain the topological database
OSPF Terminology
• Neighbor
• Adjacency Neighbors
Cost=6
ABR
BDR
DR
Non-DRAdjacencies
Router ID (RID)
Each router in OSPF needs to be uniquely identified to properly arrange them in the Neighbor tables.
Electing the DR and BDR
• OSPF sends Hellos which elect DRs and BDRs
• Router form adjacencies with DRs and BDRs in a multi-access environment
Multicast Hellos are sent and compared
Router with Highest Priority is Elected as DR
Router with 2nd Highest Priority is Elected as BDR
Configuring Loopback Interfaces
Router ID (RID): – Number by which the router is known to OSPF– Default: The highest IP address on an active interface at the
moment of OSPF process startup– Can be overridden by a loopback interface: Highest IP address
of any active loopback interface – also called a logical interface
Interface Priorities
What is the default OSPF interface priority?Router# show ip ospf interface ethernet0/0Ethernet0 is up, line protocol is upInternet Address 192.168.1.137/29, Area 4Process ID 19, Router ID 192.168.1.137, Network Type BROADCAST,Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1Designated Router (ID) 192.168.1.137, Interface address 192.168.1.137No backup designated router on this networkTimer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:06Index 2/2, flood queue length 0Next 0x0(0)/0x0(0)Last flood scan length is 0, maximum is 0Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 0, Adjacent neighbor count is 0Suppress hello for 0 neighbor(s)
Ensuring your DR
What options can you configure that will ensure that R2 will be the DR of the LAN segment?
Configuring Wildcards
If you want to advertise a partial octet (subnet), you need to use wildcards.– 0.0.0.0 means all octets match exactly– 0.0.0.255 means that the first three
match exactly, but the last octet can be any value
After that, you must remember your block sizes….
Wildcard
The wildcard address is always one less than the block size….– 192.168.10.8/30 = 0.0.0.3– 192.168.10.48/28 = 0.0.0.15– 192.168.10.96/27 = 0.0.0.31– 192.168.10.128/26 = 0.0.0.63
Wildcard Configuration of the Lab_B Router
• Lab_A• E0: 192.168.30.1/24• S0: 172.16.10.5/30
• Lab_B• E0:
192.168.40.1/24• S0:
192.168.10.10/30• S1:
192.168.10.6/30
• Lab_C• E0:
192.168.50.1/24• S1:
172.16.10.9/30
Summary
• Go through all the written and review questions
• Go over the answers with the class
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