On Feb 14, 2008, at 11:28 AM, Ben Butler wrote:
I have validated via trace in both directions as being 1 hop.
I have read another article that implies the default behaviour at the other end will to be send TTL 1 not 255 and consequently I need to configure both ends to get the session to come back up. An access list reveals all the packets I am receiving have a TTL of 0.
The session re-establishes if I configure:
neighbor 212.121.34.1 ttl-security hops >=192
<=191 and the session stays down.
Ben, After a prodding offlist I reread your message and understand what point you're making now. Indeed as you suggest above the normal configuration should be 'ttl-security hops 2' or 'ttl security hops 1'. Not for sure, but I'd have to speculate that if this is only working for you with 'ttl-security hops >= 192' perhaps your peer is setting the TTL in it's packet to 64? I believe that's the default TTL for Linux, Foundry and a couple others. Juniper's default TTL is 1 eBGP (though configurable), and 64 for iBGP, multihop, etc. IIRC. In order to implement this effectively the peer would need to be setting the transmitted TTL to 255. And my apologies if my previous message seemed a bit negative, that was certainly not my intention. -danny