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OSPF Neighbour state machine

when does the ospf speaking router hangs in exstart state.

4 REPLIES
Cisco Employee

Re: OSPF Neighbour state machine

Hi Rangha,

See if this link helps you

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094050.shtml#fifth

Plese come back if you have any doubts.

Regards,

Ankur

Re: OSPF Neighbour state machine

Check for MTU mismatch between the neighbors

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

HTH

Narayan

Re: OSPF Neighbour state machine

Hi,

One of the important issues that makes OSPF neighbor hangs on (Exstart state) is that a router is trying to make adjacency with a non DR/BDR on a segment. Offcourse those typically applied for NBMA & Broadcast OSPF Networks.

PLS try to influence the prioity at the interface level command to force the DR/BDR election.

NOTE: You may clear the OSPF process or reboot the router for the new election.

Regards,

Mohamed Sobair

Re: OSPF Neighbour state machine

Hi,

EDIT>> Here is absolute case for the Exstart OSPF neighbor state:

If you are configuring OSPF Over NBMA and hardcoding the command (IP OSPF Network point-to-multipoint) on the Hub & Spokes, Please make sure you remove all L3-to-L2 mapping from all router interfaces.

The fact that OSPF treats all links as acollection of Point-to-Point links typically possible when changing the Network type of the interface by (IP OSPF Network point-to-multipoint), by doing so, its dynamically discovering neighbors & it creats by itself L3-to-L2 maps for the neighbors , therfore , avoid static mapping which causes this problem.

HTH

Mohamed Sobair

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