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Chapter 7
Enhanced IGRP (EIGRP)
and Open Shortest Path
First (OSPF)
Link State Algorithm
Sends Update when it occurs only, link state protocols deal with three types of
tables, they are:
Neighbors table
Topology table
Route table
Open Shortest Path First (OSPF)
Allows multi-vendor deployment (Open standard) R.P
Link state R.P
Classless R.P
Supports VLSM and discontiguous networks
Has unlimited hop count
Does not make auto-summery (because of using wildcard)
AD = 110
“O” in Route Table
Used within one autonomous system (AS 1~65535)
Used with areas (2^32)
Supports authentication
Fast convergence
10.16.0.0/12
192.168.25.0/24
10.32.0.0/12
Router(config)#router ospf 10
(local significant)
Router(config-router)#network 10.16.0.0 0.15.255.255 area 1
Router(config-router)#network 10.32.0.0 0.15.255.255 area 1
Router(config-router)#network 192.168.25.0 0.0.0.255 area 0
OSPF Terminology
Link
Router ID RID
Neighbor Router
Adjacent Router
Designated Router DR
Backup Designated Router BDR
Hello protocol
Link State Advertisement LSA
Neighborship database
Topological database
OSPF areas
R1
R2
DR
BDR
R3
R4
Hierarchical Design (Areas)
Why will we use areas?
I. Fast building routing table
II. Decreasing overload on router
III. Simpler troubleshooting
Neighbors table is constructed using Hello packets
LSA Packets are transmitted between routers to construct Topological database
Shortest path tree is constructed
Dijkstra or SPF algorithm to find best for destinations with multiple paths
Results go to the route table
Network Types with OSPF
1- Point to Point
Hello interval= 10 sec.
Dead interval= 40 sec.
2- Point-to-multipoint
Hello interval= 10 sec.
Dead interval= 40 sec.
3- Broadcast (multi-access)
Hello interval= 10 sec.
Dead interval= 40 sec.
4- Non-broadcast multi-access NBMA
(Frame-Relay or X.25)
Hello interval= 30 sec.
Dead interval= 120 sec.
Electing DR and BDR
1- Priority (0~255); 1 by default
2- Router ID:
If there is only physical interface
Router(config)#int loopback 0
Router(config-if)#ip add 10.0.0.1 255.0.0.0
Router(config-if)#no shut
If there is loopback interface
OSPF Metric
Metric= cost= (10^8/B.W in bps)
Fast Ethernet= 100Mbps
Cost= 10^8/(100x10^6) =1
Ethernet= 10Mbps
Cost= 10^8/(10x10^6) =10
Serial= 1.54Mbps
Cost= 10^8/(1.54410^6) =64
Router(config)#int s0
Router(config-if)#ip ospf hello-interval 40
Router(config-if)#ip ospf dead-interval 160
Router(config-if)#ip ospf priority 25
Router(config-if)#ip ospf cost 20
Show Commands
Router#sh ip ospf
(Process ID, Area ID, RID, SPF statistics, and LSA timer information)
Router#sh ip ospf database
(Process ID, Area ID, RID, Topology Table)
Router#sh ip ospf interface
(Process ID, Area ID, RID, Interface IP address, Network type, Cost, Priority,
DR/BDR election information (if applicable), Hello and Dead timer intervals,
Adjacent neighbor information )
Router#sh ip ospf neighbor
(Process ID, Area ID, RID, Neighbors table, DR/BDR information)
DR/BDR Information
Full/
Full/DR
Full/BDR
Full/2 way DR other
Debugging OSPF
Router#debug ip ospf packet
Router#debug ip ospf hello
Router#debug ip ospf adj
Manual Summarization
Area 1
1700A
1700B
f0
.1
.3
Area 0
f0
.2
.4
2600A
s0
.1
s0/0
.2 f0/0
.1
.2
2500
s0/1
.1
s0
.2
e0
.1
.2
2600B
s1
.1
s0/0
.2 f0/0
.1
.2
Manual Summarization
In Router 2600A
2600A(config)#router ospf 10
2600A(config-router)#network 172.16.32.0 0.0.15.255 area 1
2600A(config-router)#network 172.16.48.0 0.0.15.255 area 1
2600A(config-router)#network 10.64.0.0 0.15.255.255 area 0
2600A(config-router)#area 1 range 172.16.0.0 255.255.192.0
Enhanced Interior Gateway Routing Protocol
(EIGRP)
Cisco Proprietary R.P
Hybrid (advanced distance-vector) R.P
Classless R.P
Supports VLSM and discontiguous networks
Max. hops 255 (100 by default)
Makes auto-summery by default, auto-summery can be disabled
Use composite metric (B.W, Reliability, Delay, Load, MTU)
AD = 90 (for internal EIGRP route), AD = 170 (for external EIGRP route)
“D” in Route Table
Used within one autonomous system (AS 1~65535)
Best path selection via Diffusing Update Algorithm (DUAL)
The only R.P that supports for IP, IPv6, IPX, and Apple Talk via protocol
dependent modules (PDM)
Communication via Reliable Transport Protocol (RTP)
EIGRP Packets
1- Hello Packet
2- Update Packet
3- Query Packet
4- Reply Packet
5- Acknowledge Packet
1- Hello Packet
Multicast 224.0.0.10 each (5 sec), holddown (15 sec)
2- Update Packet
Neg. IP
My Int.
Topology Table
Routing Table
Net1
Path1 Succ
Net1
Path1 Succ
Net1
Path2 F.Succ
Net2
Path1 Succ
Net1
Path3 F.Succ
Net3
Path1 Succ
Net2
Path1 Succ
Net2
Path2 F.Succ
Net3
Path1 Succ
DUAL Alg.
Neighbors Table
F.D= Feasible Distance
R.D= Reported Distance
30
F.D= Feasible Distance
F.D= Next Hop + R.D
F.D of Succ. > R.D of F. Succ (New Succ)
3- Query Packet
Holddown (180 sec), (16 x 5 sec)
4- Reply Packet
5- Acknowledge Packet
10.16.0.0/12
192.168.25.0/24
10.32.0.0/12
Router(config)#router eigrp 10
(AS)
Router(config-router)#network 10.0.0.0
Router(config-router)#network 192.168.25.0
Router(config-router)#no auto-summery
Variance Vector
New Best Path ≤ Variance x Old Best Path
Topology Table
Net1
Path1 Succ
1000
Net1
Path2 F.Succ
1500
Net1
Path3 F.Succ
2000
Net1
Path4 F.Succ
3000
New Best Path ≤ 2 x 1000
New Best Path ≤ 2000
Topology Table
Net1
Path1 Succ
1000
Net1
Path2 F.Succ
1500
Net1
Path3 F.Succ
2000
Net1
Path4 F.Succ
3000
Router(config)#eigrp 10
Router(config-router)#variance 2
Router(config-router)#maximum-paths 6
Summarization
AutomaticManual
Redistribution
EIGRP with IGRP
IGRP
1700A
1700B
f0
.1
.3
EIGRP
f0
.2
.4
2600A
s0
.1
s0/0
.2 f0/0
.1
.2
2500
s0/1
.1
s0
.2
e0
.1
.2
2600B
s1
.1
s0/0
.2 f0/0
.1
.2
Manual Summarization
1700A
1700B
f0
.1
.3
f0
.2
.4
2600A
s0
.1
s0/0
.2 f0/0
.1
.2
2500
s0/1
.1
s0
.2
e0
.1
.2
2600B
s1
.1
s0/0
.2 f0/0
.1
.2
Manual Summarization
2600A(config)#router eigrp 10
2600A(config-router)#network 172.16.0.0
2600A(config-router)#network 200.200.200.0
2600A(config-router)#no auto-summery
2600A(config-router)#exit
2600A(config)#int s0/1
2600A(config-if)#ip summary-address eigrp 10 172.16.0.0 255.255.192.0
Show and Debugging Commands
Router#sh ip eigrp neighbor
Router#sh ip eigrp topology
Router#sh ip route
Router#sh ip route rip
Router#sh ip route igrp
Router#sh ip route ospf
Router#sh ip route eigrp
Router#debug eigrp packet
Router#debug ip eigrp notification
Router#clear ip route *