Re: Migrating to SUP720

sheryl · ‎12-08-2004

I have a production cat6513 with Sup2 running and am trying to bring up a redundant 6513 w/Sup720. However, the trunk between the 2 comes up intially--then the trunk port on the production switch error disables. I suspect some issue with the config for spanning tree. Any suggestions?

Prashanth Krishnappa · ‎12-08-2004

A port can err-disable for various reasons and the switch would print the reason why it err-disabled.

Common reasons:

1)Etherchannel misconfig--If you are using etherchannels, make sure they are configured right. Also use desirable mode rather than ON

2)STP loop: Check for any loops, misconfigs which can cause loops

3)UDLD: Possible bad layer 1

Check your switch's syslog to see what the reason was and go from there.

7rbowenii · ‎12-08-2004

Building on prkrishn's input, Cisco's signalling including Ethercahnnel, trunkin others isn't always reliable. It may be that you need to set your channels to on, on manually. It might also be that you simply need to enable the err-disable side. I would try hard-setting the EC to see if it comes up, and then play with the "auto" functions of the technology.

-Bo

Prashanth Krishnappa · ‎12-08-2004

Bo

I have to disagree with you on this. If you believe you had any issues with using desirable, you need to get them addressed rather than assuming it is not reliable. Being in TAC, I have seen customers run into more issues with hardcoding etherchannel/trunking to ON rather than corner cases of issues with desirable mode.

Having said this, I do know of one bug from top of my head with desirable mode and etherchannels which is fixed now

http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCef02710

sheryl · ‎12-08-2004

Hi guys, here's what was wrong. I had etherchannel configured on the production switch, but, not on the new switch. It didn't jump out to me because the new switch is running IOS instead of CAT OS. And, we do have the trunk hard coded to on, but, are thinking about setting it to desirable later. Thanks so much for both of your inputs and suggestions. Many regards.