Subject: MD5 various keys usage

From: Dror Dror <[email-masked]>
Date: Wed, 26 Mar 2003 05:17:18 -0500

Hi,
I've been trying to configure MD5 authentication using 2 Cisco routers.
I noticed that I can configure more than one MD5 keys using the command:
     ip ospf message-digest <key_id> md5 <passowrd>

When I configured a few keys which are the same on both routers, I noticed
that the 2 routers behave differently (I opened the debug ip ospf for
logging).

Initially (after enabling ospf on both routers), both of them sent thge
HELLO packet with their youngest keys - which were different.
Then, one router kept sending the youngest key, and the other send all keys
for each OSPF packet.

I also noticed that the router sending all the keys is the one which heard
the HELLO packet first which was sent from the other router.

Does any one understand why this is done, since each OSPF packet is
replicated and sent for different keys.

Thanks
Dror

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From: Acee Lindem <[email-masked]>
Date: Wed, 26 Mar 2003 09:44:40 -0500

> replicated and sent for different keys.

Hi Dror,

This is to support changing the key on multiple routers without
losing the OSPF adjacencies (consider trying to change the key on all
routers on a LAN simultaneously). Our product has similiar
support utilizing a key chain.

Thanks,
Acee

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Acee