Solved: OSPF setup help

avilt · ‎09-27-2010

I am trying to setup OSPF in a test lab with two 2901 routers and currently I can test the OSPF adjacency only on GigabitEthernet0/0 on router A and router B. router A is in area 0 and router B in area 0 and area 1. I have connected GE0/0 from both the routers to a switch, however they do not form the OSPF adjancy. I am attaching the router config from both the routers. Appreciate your help.

Note: When I connect GigabitEthernet0/1 from either router to a different router with OSPF configuration then OSPF works fine.

Ashley Georgeson · ‎09-27-2010

Hi Avlit.

The main causes for OSPF adjacencies not forming are:

-mis-matched subnet on broadcast network (this looks okay from your config)

-mis-matched hello timers

-mis-matched ospf area id's

-mis-matched ospf area types

-no ospf interfaces configured

I would agree with the previous posts, it looks like Router A is not correctly configured (network 10.10.126.54 0.0.0.0 area 0).

To view what interfaces are participating in ospf, use the show ip ospf interface command.

I would bet that Router A will not show g0/0 as an ospf interface.

You can correct this by either amending the network statement to "network 10.10.126.53 0.0.0.0 area 0", or by configuring ospf on the interface using the "ip ospf 65182 area 0" command.

Once you are happy the interface is in ospf, then check the neighbour adjacencies. Removing authentication will clear the mist here as previously posted, once the neighbourship is up you can then apply authentication.

Regards, Ash.

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shijomon scaria · ‎09-27-2010

Hello Avit,

I am agreeing with Ashly. Instead of advertising ' network 10.10.126.53 0.0.0.0 area 0' you madi it as 'network 10.10.126.54 0.0.0.0 area 0' in router A, correct this first and check.

Otherwise advertise the network intead of interface ip address.

Regards,

Shijo.

View solution in original post

sumitava123 · ‎09-27-2010

Hi Avilt ,

I can see that u have published x.x.88.0 network in area 0 in router a and in area 1 in router B.Thats why no neighborship is forming between them.

Hope this helps .

Cheers

Sumit

Giuseppe Larosa · ‎09-27-2010

Hello Avillt,

I recommend to start testing without OSPF authentication, the error may be an unwanted additional space in MD5 password and so on.

After OSPF adjacency is formed without authentication you can add it it again

Also notice that the two ge0/1 are in different IP subnets (but this is wanted I guess)

Edit:

clearly as Sumit noted area-id must match but for ge0/0 it is fine both are in area 0.

Hope to help

Giuseppe

sumitava123 · ‎09-27-2010

Adding to what giuslar has informed I have also found that you have assigned IP address 10.10.126.53 on g0/0 but published network 10.10.126."54" 0.0.0.0(<

Sumit

avilt · ‎09-27-2010

Let me explain you the topolgy in detail.

GigabitEthernet0/0 interfaces on both router A and router B are in the same segment (10.10.126.0/192) and I have put them in area 0. However GigabitEthernet0/1 interfaces (ISP links) are in the different segment on router A (area 0) and router B (area 1).

I took two spare routers and tested ospf with GigabitEthernet0/1 segment on both rouer A and router B, it works fine. Why is that OSPF adjency is not forming on GigabitEthernet0/0 segment?

I would like to connect area 0 and area 1 between router A and router B on 10.10.126.0 segment.

Ashley Georgeson · ‎09-27-2010

Hi Avlit.

The main causes for OSPF adjacencies not forming are:

-mis-matched subnet on broadcast network (this looks okay from your config)

-mis-matched hello timers

-mis-matched ospf area id's

-mis-matched ospf area types

-no ospf interfaces configured

I would agree with the previous posts, it looks like Router A is not correctly configured (network 10.10.126.54 0.0.0.0 area 0).

To view what interfaces are participating in ospf, use the show ip ospf interface command.

I would bet that Router A will not show g0/0 as an ospf interface.

You can correct this by either amending the network statement to "network 10.10.126.53 0.0.0.0 area 0", or by configuring ospf on the interface using the "ip ospf 65182 area 0" command.

Once you are happy the interface is in ospf, then check the neighbour adjacencies. Removing authentication will clear the mist here as previously posted, once the neighbourship is up you can then apply authentication.

Regards, Ash.

avilt · ‎09-27-2010

Thank You. I was using HSRP ip in the network command, rectified it to reflect the subnet.

I will also add md5 authentication for HSRP.

shijomon scaria · ‎09-27-2010

Hello Avit,

I am agreeing with Ashly. Instead of advertising ' network 10.10.126.53 0.0.0.0 area 0' you madi it as 'network 10.10.126.54 0.0.0.0 area 0' in router A, correct this first and check.

Otherwise advertise the network intead of interface ip address.

Regards,

Shijo.