Hey. Wow, it's been a while since I've been here. I passed my CCNA back in August, but I've been so busy with school that I haven't had time to start studying CCNP material much. Ah well, I'm only a year and two thirds of semester away from graduation (Computer Science).
How has everyone been? Did mike try the CCIE lab again? I wish him the best of luck either way.
Anyway what made me stop in was an issue that cam up at work yesterday and I'm not really sure why this happened. Maybe someone here can explain it. Here's the Reader's Digest version:
A student calls up saying his port isn't working. Helpdesk sends it down to networking because his machine doesn't appear to work in his roommates port either, and now his roommate's port doesn't work at all. The caller said that the trouble started right after he booted wit an Ubuntu liveCD. I go down there and his setup is network port -> hub (that's actual layer 1 hub) -> pc, xbox
So, I figure the hub somehow pissed off the switch (it's a Catalyst 3560G PoE) and the switch turned it off. I go log into the switch and sure enough it was errdisabled. Now, since we don't have any other way to check why it was errdisabled, I went and checked the tacacs logs (tacas is really really cool, by the way) and they say it was. Here are the actual entries, IP addresses obfuscated because I'm paranoid even though they're 10.x.x.x addresses
Feb 14 09:35:51 <IP> 1676: 4w0d: %PM-4-ERR_DISABLE: loopback error detected on Gi0/10, putting Gi0/10 in err-disable state
Feb 15 14:30:05 <IP> 1748: 4w1d: %PM-4-ERR_DISABLE: loopback error detected on Gi0/4, putting Gi0/4 in err-disable state
That seemed rather unusual since he claims he never had the hub connected to both ports at the same time. Also, the time stamps are different so it doesn't seem like he had the thing plugged into two ports at the same time. I presumed it was the hub that was causing all of this trouble, reset his port and told him to go buy a desktop switch.
However, while testing, the second I plugged that hub in, the port shut right down again. I just don't see how the switch saw the keepalive message, which Cisco says causes loop disables out the same port it sensed, unless the hub is somehow broken and sending messages out every port including the one it cam in on.
But, I still don't understand how his port ended up in a loop error state or why it would make a difference what OS he used. I'm a bit skeptical that the problem really started right when he booted that liveCD. Anyone have any ideas on this one? It just seems odd.
