[c-nsp] Using 'shutdown' versus pulling the cable

[Dale Shaw]

Hi all,

I'm working on some failover test scenarios and I'm trying to
determine if issuing a 'shutdown' command on a router's Ethernet
interface is effectively identical, from the perspective of the
attached switch, as removing the cable.

Here's a simplified topology:

R1-Fa0/0 -- Fa1/0/1-SW1

Assume R1's Fa0/0 interface is directly connected to SW1's Fa1/0/1
interface, and Fa1/0/1 is configured as a routed port ("no
switchport"). R1 and SW1 are EIGRP neighbours.

Is the 'shutdown' command somehow 'cleaner' or more graceful than
yanking the cable? For example, does IOS do any 'nice' things like
send EIGRP goodbye messages before *really* shutting down the
interface? Anything similar happening at lower layers? This requires
insight into IOS behaviour that I don't have and I'm not sure how to
get within any reasonable time frame (read: without cracking out the
packet capture tool).

We don't have remote power-off/power-on capabilities so this is all
about assessing whether we need an on-site presence to simulate loss
of power. If 'shutdown' on R1 is the same as pulling the cable, and
SW1's response will be the same, that's great. If it's not the same,
it's not a valid simulation.

Hopefully this hasn't been covered before. The key words involved make
it difficult to search on.

Cheers,
Dale