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Cisco Portchannel Fix

These instructions discuss what to do when an ancient Cisco 6500 series switch (e.g., Cisco3) starts having problems when snmpit tries to manipulate vlans on a particular port channel.

Symptom: Snmpit fails to setup portchannel vlans, and may log errors such as the following:

*** WARNING: snmpit_test:
***   SNMP SET failed - In snmpit_test
***   SNMPIT set failed for device cisco3 (try 10 of 10)
***   Variable was [vlanTrunkPortVlansEnabled,228450,NOSUCHINSTANCE***   
      Returned (undefined), ErrorNum was 12
***   Error string is: inconsistentValue (The set value is illegal or 
      unsupported in some way)
RPC::Async::Server: Disconnecting client for error: SNMP SET failed - In 
      snmpit_test
SNMPIT set failed for device cisco3 (try 10 of 10)
Variable was [vlanTrunkPortVlansEnabled,228450,NOSUCHINSTANCEReturned 
      (undefined), ErrorNum was 12
Error string is: inconsistentValue (The set value is illegal or unsupported 
      in some way)
*** ERROR: snmpit_test: RPC::Async::Client: server disconnected
*** ERROR: tbswap: Failed to set up VLANs.

The recipe for fixing this up follows below.  THIS IS AN EXAMPLE - DO
NOT USE VERBATIM!  You need to insert the proper port information.
Use "show startup-config" to find this info.

First, turn off the port channel and turn it back on.

  set port channel 2/9-12 mode off
  set port channel 2/9-12 mode on

Next, wipe and restore the trunk config for each port in the port
channel.  You'll need to grab the currently configured set of vlans
from the running config. You should be able to just copy/paste what is
in the running config for this step.

  clear trunk 2/9  2-9,11-291,293-304,306-312,...
  set trunk 2/9  2-9,11-291,293-304,306-312,...
  clear trunk 2/10  2-9,11-291,293-304,306-312,...
  set trunk 2/10  2-9,11-291,293-304,306-312,...
  clear trunk 2/11  2-9,11-291,293-304,306-312,...
  set trunk 2/11  2-9,11-291,293-304,306-312,...
  clear trunk 2/12  2-9,11-291,293-304,306-312,...
  set trunk 2/12  2-9,11-291,293-304,306-312,...

Now create an experiment with a LAN that spans across this channel to
test that things are fixed.