OSPF and EIGRP

[tariq.hussain.pk]

Hi all

In a network ospf routing protocol is configured then eigrp has been configure by administrator.

Eigrp has less AD so EIGRP will send routing updates.IS ospf try to maitain there routing and topology tables or it is disabled.

thanks in advance

[kamlesh.sharma]

Hi tariq,

Yes you are right when you configure EIGRP over ospf all the router will use EIGRP learned route bcos of AD.

Yes OSPF will still be running there in router and if there is any problem with EIGRP than router will install ospf learned route in the routing table.

HTH

kamlesh

please rate helpfull reply

[minumathur]

I think ospf is disable , because a protocol which has less AD , that protocol create routing table in router, so in your case you can't find any ospf route in routing table

[tariq.hussain.pk]

Thanx for the reply

but the problem is that i received the ospf updates like that

"Jul 3 10:53:28.642: %OSPF-5-ADJCHG: Process 1, Nbr 172.16.23.2 on Serial1/3 fr

om LOADING to FULL, Loading Done

Jul 3 11:23:23.056: %OSPF-5-ADJCHG: Process 1, Nbr 172.16.23.2 on Serial1/3 fro

m EXSTART to DOWN, Neighbor Down: Too many retransmitions"

Why I received these type of messages.

[ariela]

Hi,

first of all, OSPF works always, even if in your topology the AD is worst. You have anyway a topology table, and an adjacency table.

In Exstart state, the neighboring routers establish a master/slave relationship and determine the initial database descriptor (DBD) sequence number to use while exchanging DBD packets. In other words, the routers and their DR and BDR establish a master-slave relationship and choose the initial sequence number for adjacency formation. The router with the higher router ID becomes the master and starts the exchange, and as such, is the only router that can increment the sequence number. Note that one would logically conclude that the DR/BDR with the highest router ID will become the master during this process of master-slave relation. Remember that the DR/BDR election might be purely by virtue of a higher priority configured on the router instead of highest router ID. Thus, it is possible that a DR plays the role of slave. And also note that master/slave election is on a per-neighbor basis.

About your problem: adjacency is out, maybe MTU mismatch? Check your serial link.

for more infos:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f0d.shtml

use 'debug ip ospf adj'

Hope this helps

Regards

Andrea

[Richard Burts]

The suggestion that OSPF is disabled because of higher AD is incorrect. Andrea is quite correct that OSPF will still run, will send hello messages, and will build adjacencies. It does not matter whether the OSPF routes make it into the routing table or not, but OSPF is still active.

If there is an MTU mismatch I am not sure that the neighbor relationship would be formed. But I agree that the messages indicate that there is some issue on the serial interface. the suggestion of debug ip ospf adj is a good place to start.

HTH

Rick