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New Member

OSPF neigbour routers not exchanging information

Hello,

I am  newbie network administrator at work coming in with a linux backgroud so I am new to routing protocols.

I have to setup two routers, one called Montreal and the other Toronto.

We will be using a frame relay eventually but for testing purposes I just wanted to connect the two routers with a serial cable to test for connectivity.

I set up a serial cable, configured clock rate, and ran ospf. The two do not even seem to be exchaning hello packets.

I spent hours trying to figure out what is wrong but to no avail.

I attach my VLSM scheme as well as 5.3.1 packet analyzer file. If someone could point out the problem so I could fix it I wold appreciate it.

Thanks,

  • WAN Routing and Switching
13 REPLIES
Hall of Fame Super Blue

OSPF neigbour routers not exchanging information

Mohit

Can you ping one router from the other ?

Have you included the subnet of the serial link under your OSPF config on both routers.

If yes to both answers can you post the router configs as text as some of use can't read packet tracer files

Jon

New Member

Re: OSPF neigbour routers not exchanging information

Hi John,

I can ping from one serial interface to another. I checked that

As for your second concern, I just advertised the networks assigned to the subinterfaces of fa0/0 on both routers as these are the interfaces that have PC's and servers attached to them.

In my limited training, I was never told that we had to advertise the subnet of the serial interfaces themselves. Does  it have to be advertised?

I am more of a Linux Administrator being trained to do network administration hence my "simple" questions.

I am not on a windows machine so I cannot run packet anayzer so what I can give you is the VLSM outline detailing the networks of the routers:

Router1:

192.168.100.0 with a subnet mask of 255.255.255.192

192.168.100.128 with a subnet mask of 255.255.255.224

192.168.100.192 with a subnet mask of 

255.255.255.240

Router 2:

192.68.100.64          

255.255.255.19

192.168.100.128

255.255.255.224

192.168.100.208

255.255.255.240

The serial connections are on these IP's and subnet mask:

192.168.100.225 and 192.168.100.226 with subnet mask

255.255.255.252

Do you think the problem is that the subnet with the serial connections was not advertised?

Purple

OSPF neigbour routers not exchanging information

Hi,

in every IGP(RIP,EIGRP,OSPF), the network command is used to enable the routing protocol on the interfaces whose IP address falls into the network command and it will also advertise those subnets.

Regards.

Alain

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New Member

OSPF neigbour routers not exchanging information

Thank you for your answer Alain. So if I follow you correctly I have to make sure that the networks having my PC'/Servers are advertised as well as the subnets of the serial interfaces?

--Mohit

Purple

OSPF neigbour routers not exchanging information

Hi,

if you want them to be reachable via OSPF yes you must but as there is no OSPF neighbour on the other side  you should also in the routing process declare these interfaces as passive.

eg:

router ospf 1

network x.x.x.x area x

passive-interface fx/x

Regards.

Alain

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New Member

OSPF neigbour routers not exchanging information

There is just one serial connection between serial 0/0/0 on router 1 and between serial 0/0/0 on router 2. fa0/0 on both routers are in use and that's it. The passive interface directive is not mandatory is it?

Purple

OSPF neigbour routers not exchanging information

Hi,

no it's not mandatory.this is a security feature here because then these networks will still be advertised but the router won't be sending OSPF messages and so there won't be no adjacency on these links.

Regards.

Alain

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New Member

OSPF neigbour routers not exchanging information

How will the networks on the other fa interfaces be advertised if I do not explicity advertise them with the network command?

Purple

Re: OSPF neigbour routers not exchanging information

Hi,

What do you mean? You want full reachability from end to end with OSPF?

I'm gonna take a look at your PT file but I encourage you to use GNS3 to test routing because PT is a tool mainly used for CCNA and there a a lot of things that ain't working  and you don't have all the debug commands available.

EDIT: ok just enable OSPF on the serial connecting the 2 routers on both and the other network commands are comprising the subnets from the subinterfaces and so the subnets from the machines on each LAN.You can ping all Toronto's machines from Montreal's machines so there is end-to-end connectivity.

Regards.

Alain

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