ISSUE with installing Wic cards

[bobdempsey]

On the 2600 series the 2 WIC slots are labeled W0 and W1 from right to left. If you put a single card in slot W1 (the slot near the middle of the chassis) it will come up as S0/0.

For example, when I put a WIC 1DSU T1 card in slot W1 in my 2621 by itself, it comes up as S0/0:

Router#sh int s0/0
Serial0/0 is administratively down, line protocol is down
Hardware is PQUICC with Fractional T1 CSU/DSU

I can then configure s0/0 as a T1.

If I then shut the router down and install a WIC 1T in slot W0, the hardware renumbers the interfaces and the WIC 1T comes up a s0/0, not because the WIC 1T somehow "takes over" but becuase I put it in slot W0, and IOS prefers to give a WIC in slot W0 the s0/0 interface:

Router#sh int s0/0
Serial0/0 is administratively down, line protocol is down
Hardware is PowerQUICC Serial

Router#sh int s0/1
Serial0/1 is administratively down, line protocol is down
Hardware is PQUICC with Fractional T1 CSU/DSU

But now my startup-config no longer matches the installed hardware and things won't work right. You either have to fix the startup-config or fix the hardwae config by swapping the cards. You can avoid this by always populating slot W0 (the one nearest the power cord) first.