Home To Know Networking OSPF (Open Shortest Path First) Part- 2

OSPF (Open Shortest Path First) Part- 2

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OSPF (Open Shortest Path First) Part- 2

OSPF (Open Shortest Path First) Topology

OSPF (Open Shortest Path First) Topology
OSPF (Open Shortest Path First) Topology

R1 (config) #int fa0/0
R1 (config-if) #ip add 192.168.101.1 255.255.255.0
R1 (config-if) #no shut
R1 (config-if) #int s0/0
R1 (config-if) #ip add 192.168.1.1 255.255.255.0
R1 (config-if) #no shut


R2 (config) #int fa0/0
R2 (config-if) #ip add 192.168.102.1 255.255.255.0
R2 (config-if) #no shut
R2 (config-if) #int s0/0
R2 (config-if) #ip add 192.168.1.2 255.255.255.0
R2 (config-if) #no shut
R2 (config-if) #int s0/1
R2 (config-if) #ip add 192.168.2.1 255.255.255.0
R2 (config-if) #no shut


R3 (config) #int fa0/0
R3 (config-if) #ip add 192.168.103.1 255.255.255.0
R3 (config-if) #no shut
R3 (config-if) #int s0/0
R3 (config-if) #ip add 192.168.2.2 255.255.255.0
R3 (config-if) #no shut
R3 (config-if) #int s0/1
R3 (config-if) #ip add 192.168.3.1 255.255.255.0
R3 (config-if) #no shut


R4 (config) #int fa0/0
R4 (config-if) #ip add 192.168.104.1 255.255.255.0
R4 (config-if) #no shut
R4 (config-if) #int s0/0
R4 (config-if) #ip add 192.168.3.2 255.255.255.0
R4 (config-if) #no shut
R4 (config-if) #int s0/1
R4 (config-if) #ip add 192.168.4.1 255.255.255.0
R4 (config-if) #no shut
R4 (config-if) #int s0/2
R4 (config-if) #ip add 192.168.7.1 255.255.255.0
R4 (config-if) #no shut


R5 (config) #int fa0/0
R5 (config-if) #ip add 192.168.105.1 255.255.255.0
R5 (config-if) #no shut
R5 (config-if) #int s0/0
R5 (config-if) #ip add 192.168.4.2 255.255.255.0
R5 (config-if) #no shut
R5 (config-if) #int s0/1
R5 (config-if) #ip add 192.168.5.1 255.255.255.0
R5 (config-if) #no shut
R5 (config-if) #int lo1
R5 (config-if) #ip add 170.50.1.1 255.255.255.0
R5 (config-if) #int lo2
R5 (config-if) #ip add 170.50.2.1 255.255.255.0
R5 (config-if) #int lo3
R5 (config-if) #ip add 170.50.3.1 255.255.255.0
R5 (config-if) #int lo4
R5 (config-if) #ip add 170.50.4.1 255.255.255.0
R5 (config-if) #int lo5
R5 (config-if) #ip add 170.50.5.1 255.255.255.0


R6 (config) #int fa0/0
R6 (config-if) #ip add 192.168.106.1 255.255.255.0
R6 (config-if) #no shut
R6 (config-if) #int s0/0
R6 (config-if) #ip add 192.168.5.2 255.255.255.0
R6 (config-if) #no shut
R6 (config-if) #int s0/1
R6 (config-if) #ip add 192.168.6.1 255.255.255.0
R6 (config-if) #no shut


R7 (config) #int fa0/0
R7 (config-if) #ip add 192.168.107.1 255.255.255.0
R7 (config-if) #no shut
R7 (config-if) #int s0/0
R7 (config-if) #ip add 192.168.6.2 255.255.255.0
R7 (config-if) #no shut
R7 (config-if) #int lo1
R7 (config-if) #ip add 170.70.1.1 255.255.255.0
R7 (config-if) #int lo2
R7 (config-if) #ip add 170.70.2.1 255.255.255.0
R7 (config-if) #int lo3
R7 (config-if) #ip add 170.70.3.1 255.255.255.0
R7 (config-if) #int lo4
R7 (config-if) #ip add 170.70.4.1 255.255.255.0
R7 (config-if) #int lo5
R7 (config-if) #ip add 170.70.5.1 255.255.255.0


R8 (config) #int fa0/0
R8 (config-if) #ip add 192.168.108.1 255.255.255.0
R8 (config-if) #no shut
R8 (config-if) #int s0/0
R8 (config-if) #ip add 192.168.7.2 255.255.255.0
R8 (config-if) #no shut
R8 (config-if) #int lo1
R8 (config-if) #ip add 170.80.1.1 255.255.255.0
R8 (config-if) #int lo2
R8 (config-if) #ip add 170.80.2.1 255.255.255.0
R8 (config-if) #int lo3
R8 (config-if) #ip add 170.80.3.1 255.255.255.0
R8 (config-if) #int lo4
R8 (config-if) #ip add 170.80.4.1 255.255.255.0
R8 (config-if) #int lo5
R8 (config-if) #ip add 170.80.5.1 255.255.255.0

Now we will run routing protocol on each router

R1 (config) #router ospf 100
R1 (config-router) #router-id 1.1.1.1
R1 (config-router) #int fa0/0
R1 (config-if) #ip ospf 100 area 2
R1 (config-router) #int s0/0
R1 (config-if) #ip ospf 100 area 2


R2 (config) #router ospf 100
R2 (config-router) #router-id 2.2.2.2
R2 (config-router) #int fa0/0
R2 (config-if) #ip ospf 100 area 2
R2 (config-router) #int s0/0
R2 (config-if) #ip ospf 100 area 2
R2 (config-router) #int s0/1
R2 (config-if) #ip ospf 100 area 1


R3 (config) #router ospf 100
R3 (config-router) #router-id 3.3.3.3
R3 (config-router) #int fa0/0
R3 (config-if) #ip ospf 100 area 1
R3 (config-router) #int s0/0
R3 (config-if) #ip ospf 100 area 1
R3 (config-router) #int s0/1
R3 (config-if) #ip ospf 100 area 0


R4 (config) #router ospf 100
R4 (config-router) #router-id 4.4.4.4
R4 (config-router) #int fa0/0
R4 (config-if) #ip ospf 100 area 0
R4 (config-router) #int s0/0
R4 (config-if) #ip ospf 100 area 0
R4 (config-router) #int s0/1
R4 (config-if) #ip ospf 100 area 0
R4 (config) #router ei 100
R4 (config-router) #no auto-summary
R4 (config-router) #network 192.168.7.0


R5 (config) #router ospf 100
R5 (config-router) #router-id 5.5.5.5
R5 (config-router) #int fa0/0
R5 (config-if) #ip ospf 100 area 3
R5 (config-router) #int s0/0
R5 (config-if) #ip ospf 100 area 0
R5 (config-router) #int s0/1
R5 (config-if) #ip ospf 100 area 3
R5 (config-router) #int lo1
R5 (config-if) #ip ospf 100 area 3
R5 (config-router) #int lo2
R5 (config-if) #ip ospf 100 area 3
R5 (config-router) #int lo3
R5 (config-if) #ip ospf 100 area 3
R5 (config-router) #int lo4
R5 (config-if) #ip ospf 100 area 3
R5 (config-router) #int lo5
R5 (config-if) #ip ospf 100 area 3


R6 (config) #router ospf 100
R6 (config-router) #router-id 6.6.6.6
R6 (config-router) #int s0/0
R6 (config-if) #ip ospf 100 area 3
R6 (config-router) #router ei 200
R6 (config-router) #no auto-summary
R6 (config-router) #network 192.168.6.0
R6 (config-router) #network 192.168.106.0


R7 (config) #router ei 200
R7 (config) #no auto-summary
R7 (config) #network 0.0.0.0


R8 (config) #router ei 100
R8 (config-router) #no auto-summary
R8 (config-router) #network 0.0.0.0


R1#sh ip route

Here we can see only one route, because R1 is in Area 2 and it is not directly connected with area 0. Each area must be connected with area 0. Now we will create virtual link to connect area 2 with area 0.

Virtual link would be created on edge to edge router

R2 (config) #router os 100
R2 (config-router) #area 1 virtual link 3.3.3.3


R3 (config) #router os 100
R3 (config-router) #area 1 virtual link 2.2.2.2


R1#sh ip route os
R1#ping 192.168.5.2 successful
R1#ping 172.30.1.1 successful

OSPF creates three tables

R1#sh ip os neighbor
R1#sh ip os database
R1#sh ip route os

Passive-Interface

R1 (config) #router os 100
R1 (config-router) #passive-interface default

This command will apply on each interface.

R1 (config-router) #no passive-interface s0/0

If we want to make only fa0/0 passive then we need to apply only on fa0/0

R1 (config) #router os 100
R1 (config-router) #passive-interface fa0/0

OSPF Authentication

R1 (config) #int s0/0
R1 (config-if) #ip ospf authentication message-digest
R1 (config-if) #ip ospf message-digest key 1 md-5 Mani
R1#sh ip ospf neighbor

After 40 sec neighborship will be down.

R1#debug ip ospf events

Mismatch authentication

R1#un all

R2 (config) #int s0/0
R2 (config-if) #ip ospf authentication message-digest
R2 (config-if) #ip ospf message-digest key 1 md-5 abc

Neighborship will be up.

Now we will check hello & hold timers

R1#sh ip ospf int s0/0

Hello – 10 sec Dead 40 sec

We will change the timer

R1 (config) #int s0/0
R1 (config-if) #ip ospf hello-interval 5
R1#sh ip os int s0/0

Hello 5 Dead 20

We can see if we change hello, Dead will be changed automatically.

R1#sh ip os ne

Neighborship will be break. In ospf hello and dead interval must match for the neighborship.

R1#clear ip os process

Yes

R1#debug ip os events

Mismatch hello parameter

R– Received

C– Configured

R2 (config) #int s0/0
R2 (config-if) #ip os hello-interval 5

Neighborship will be build-up

Now we will change Dead interval

R2 (config) #int s0/0
R2 (config-if) #ip os dead-interval 15
R2#sh ip int os s0/0

When we change dead, hello will not change automatically.

R2#debug ip os events
R2#un all


R1 (config) #int s0/0
R1 (config-if) #ip os dead-interval 15

Neighborship will be buildup. Now OSPF domain should be communicated with EIGRP 100.

For that we will perform redistribution

R4 (config) #router os 100
R4 (config-router) #redistribute ei 100


R1#sh ip route os

E2 – 192.168.108.0

E2 – 192.168.7.0

By default it would advertise classfull network. If we want to advertise classless also then we need to add a keyword “Subnets”.

R4 (config) #router os 100
R4 (config-router) #redistribute ei 100 subnets


R1#sh ip route os

Now we can see the classless network also. 172.50.0.0.

O – OSPF

E2 – External (Metric type 2)

Now we can see external routes metric is 20 on each route. That is not true.

Default metric 20

Here internal cost should be added.

R4 (config) #router os 100
R4 (config-router) #redistribute ei 100 subnets metric-type 1

Metric type 1 means add internal cost also when you exchange routes.

R1#sh ip route

OE – 172.30.4.0 (110/212) previously it was 20.

Above we redistributed EIGRP in ospf

Now we will redistribute ospf in EIGRP

R4 (config) #router ei 100
R4 (config-router) #redistribute os 100 metric 1 1 1 1 1


R1#ping 172.30.1.1 successful
R1#sh ip route

Here we can see two types of route, External routes and Inter area routes.

There are two types of summarization:

  • External Summarization (ASBR)
  • Inter Area Summarization (ABR)

ASBR router is router no 4 here.

R4 (config) #router os 100
R4 (config-router) #summary-address 172.80.0.0 255.255.248.0


R1#sh ip route

Here we can see only one route of 172.80.0.0/21

R1#ping 172.80.1.1
R1#ping 172.80.1.1

Successful

Now we will remove it.

R4 (config) #router os 100
R4 (config-router) #no summary-address 172.80.0.0 255.255.248.0

Now we will summarize inter area routes

It will perform on ABR.

We will summarize the network 172.50.0.0 network. For that ABR is R5.

R5 (config) #router os 100
R5 (config-router) #area 3 range 172.50.0.0 255.255.248.0


R1#sh ip route os

Here we can see summarized inter area routes.

R1#ping 172.50.1.1
R1#ping 172.50.1.1

Successful

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