[c-nsp] shut interfaces become enabled for some secs while reloading

Tassos Chatzithomaoglou achatz at forthnet.gr
Thu Sep 25 06:08:17 EDT 2008


Has anyone met the above problem?

I'm trying a 7200/G2 with 12.2(31)SB13 and i noticed that while reloading it, the shuted interfaces come up for 2 secs, 
which is more than enough time to send packets through them (having portfast enabled on the switch port).

I guess the config is parsed sequentially, so if the "shutdown" command follows the "ip address x.x.x.x" command (which 
they do when doing "sh run"), ip connectivity is established first.

The problem with the above is that if you have to prepare a second router having identical config with another one 
(keeping the interfaces of the second router in the shutdown state), you end up having duplicate ips for a while (in my 
case 2 secs) when reloading the second router. This small time is more than enough to make the hell out of arp/mac tables!!!

I know there are many ways to avoid all this mess (remove/change ips, shut switch ports instead of router ports, etc), 
but i was mainly wondering if all this is expected/normal behavior.

-- 
Tassos


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