Re: running ospf between routers via ethernet

ahmadbilal · ‎10-29-2004

hi,

I have connected a cisco router and a nortel router together with ospf running.The neighbor state shows

INIT/DROTHER

If i shut no shut the ethernet port the neighbor state goes to full/DROTHER but goes back to INIT/drother

##### the output of debug ip ospf adj is as follows ###

5w4d: OSPF: Interface Ethernet1/0 going Up

5w4d: OSPF: 2 Way Communication to 10.18.1.2 on Ethernet1/0, state 2WAY

5w4d: OSPF: Rcv DBD from 10.18.1.2 on Ethernet1/0 seq 0x1337861 opt 0x2 flag 0x7

len 32 mtu 0 state 2WAY

5w4d: OSPF: Nbr state is 2WAY

5w4d: OSPF: end of Wait on interface Ethernet1/0

5w4d: OSPF: DR/BDR election on Ethernet1/0

5w4d: OSPF: Elect BDR 10.18.1.1

5w4d: OSPF: Elect DR 10.18.1.1

5w4d: OSPF: Elect BDR 0.0.0.0

5w4d: OSPF: Elect DR 10.18.1.1

5w4d: DR: 10.18.1.1 (Id) BDR: none

5w4d: OSPF: Send DBD to 10.18.1.2 on Ethernet1/0 seq 0x1943 opt 0x52 flag 0x7 le

n 32

5w4d: OSPF: No full nbrs to build Net Lsa for interface Ethernet1/0

5w4d: OSPF: Rcv DBD from 10.18.1.2 on Ethernet1/0 seq 0x1337861 opt 0x2 flag 0x7

len 32 mtu 0 state EXSTART

5w4d: OSPF: NBR Negotiation Done. We are the SLAVE

5w4d: OSPF: Send DBD to 10.18.1.2 on Ethernet1/0 seq 0x1337861 opt 0x52 flag 0x2

len 1052

5w4d: OSPF: Rcv DBD from 10.18.1.2 on Ethernet1/0 seq 0x1337862 opt 0x2 flag 0x3

len 512 mtu 0 state EXCHANGE

5w4d: OSPF: Send DBD to 10.18.1.2 on Ethernet1/0 seq 0x1337862 opt 0x52 flag 0x0

len 32

5w4d: OSPF: Database request to 10.18.1.2

5w4d: OSPF: sent LS REQ packet to 172.16.253.246, length 24

5w4d: OSPF: Rcv DBD from 10.18.1.2 on Ethernet1/0 seq 0x1337863 opt 0x2 flag 0x3

len 512 mtu 0 state EXCHANGE

5w4d: OSPF: Send DBD to 10.18.1.2 on Ethernet1/0 seq 0x1337863 opt 0x52 flag 0x0

len 32

5w4d: OSPF: No full nbrs to build Net Lsa for interface Ethernet1/0

5w4d: OSPF: Rcv DBD from 10.18.1.2 on Ethernet1/0 seq 0x1337864 opt 0x2 flag 0x1

len 72 mtu 0 state EXCHANGE

5w4d: OSPF: Exchange Done with 10.18.1.2 on Ethernet1/0

5w4d: OSPF: Synchronized with 10.18.1.2 on Ethernet1/0, state FULL

*Apr 9 17:26:01: %OSPF-5-ADJCHG: Process 20, Nbr 10.18.1.2 on Ethernet1/0 from

LOADING to FULL, Loading Done

5w4d: OSPF: Send DBD to 10.18.1.2 on Ethernet1/0 seq 0x1337864 opt 0x52 flag 0x0

len 32

5w4d: OSPF: Build router LSA for area 0, router ID 10.18.1.1, seq 0x800006F3

5w4d: OSPF: Build network LSA for Ethernet1/0, router ID 10.18.1.1

5w4d: OSPF: Build network LSA for Ethernet1/0, router ID 10.18.1.

show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

10.18.1.2 0 FULL/DROTHER 00:00:38 172.18.1 .1Ethernet1/0

5w4d: OSPF: Cannot see ourself in hello from 10.18.1.2 on Ethernet1/0, state INI

T

5w4d: OSPF: Neighbor change Event on interface Ethernet1/0

5w4d: OSPF: DR/BDR election on Ethernet1/0

5w4d: OSPF: Elect BDR 0.0.0.0

5w4d: OSPF: Elect DR 10.18.1.1

5w4d: DR: 10.18.1.1 (Id) BDR: none

5w4d: OSPF: Build router LSA for area 0, router ID 10.18.1.1, seq 0x800006F4

5w4d: OSPF: No full nbrs to build Net Lsa for interface Ethernet1/0

5w4d: OSPF: Build network LSA for Ethernet1/0, router ID 10.18.1.1

help.

seilsz · ‎10-29-2004

There appears to be a problem with your OSPF Hello packets making it over to the Nortel router. Do you get a response from the Nortel router if you ping 224.0.0.5?

~Zach

Richard Burts · ‎10-29-2004

Before I talk about what the debug shows, lets review a couple of things about how OSPF works. OSPF routers send hello packets through the interface which are used to find neighbors and keep track of adjacencies. In the hello packet there is a field which identifies the DR on the segment (if one has been elected), a field which identifies the BDR on teh segment (if one has been elected), and a field which identifies all of the neighbors that we know about on the segment.

What we see is that the interface comes up. The router elects itself as BDR and then as DR. This is normal behavior when a router comes up and does not recognize existing neighbors on the segment. then the router receives a hello from the Nortel. This triggers building an adjacency based on the exchange of DBD records. Your router believes that the exchange is complete. A couple of significant records are these:

5w4d: OSPF: Exchange Done with 10.18.1.2 on Ethernet1/0

5w4d: OSPF: Synchronized with 10.18.1.2 on Ethernet1/0, state FULL

*Apr 9 17:26:01: %OSPF-5-ADJCHG: Process 20, Nbr 10.18.1.2 on Ethernet1/0 from

LOADING to FULL, Loading Done

which indicate that the process is complete and the router believes that it has a complete neighbor. This is also show in the show command which you did:

show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

10.18.1.2 0 FULL/DROTHER 00:00:38 172.18.1 .1Ethernet1/0

This says that there is a neighbor with a FULL adjacency.

I notice one thing that is a little bit odd. Your router believes that it is the DR. It has found a neighbor but the neighbor is not the BDR. If there are only two routers on the segment, I would expect the other router to be elected BDR. I am not sure if theis is related to the problem or not.

Having built the neighbor relationship, your router will list the Nortel router as a neighbor in its hello. And it expects the Nortel router to list you in the hello. But your router receives a hello from the Nortel router which does not list you. Based on this the router tears down the neighbor relationship, it would flush anything that it had learned from the Nortel router.

I am not sure what the problem is, but I think you are more likely to find it on the Nortel router than on the Cisco. My suspicion is that there may be some parameter mismatch between the routers which prevents the Nortel from completing the neighbor relationship.

One other comment is that with the log records having a timestamp showing uptime in weeks and days, it is hard to see the time relationship of what is happening. If you would configure service timestamps log datetime msec, it would be easier to see the time relationships.

HTH

Rick

HTH

Rick

ahmadbilal · ‎10-30-2004

hi,

I agree tht it is odd tht we have aDR but no BDR.I tried forcing the cisco router not to take part by giving a priority of 0.the change was that it got suck in two-way/DROTHER state.Is it necessary to have a DR and a BDR for broadcast media.

I will check the nortel router settings and get back.

regards and thanks

Richard Burts · ‎10-31-2004

On a broadcast media, after a router discovers a neighbor, they will go through the process of forming an adjacency only if one of the routers is the DR or the BDR. So if the Cisco is neither DR nor BDR and the Nortel does not seem to be, then there will be no adjacency and they will not learn each others routes.

From the debug messages I think it is most likely that the problem in on the Nortel router. It might be helpful if you could post the config from the Cisco router.

Let us know what you find on the Nortel.

HTH

Rick

HTH

Rick