STP Issue

[Rob Yamry]

Over the weekend I started getting many events like the following in the logs:

----  Reverse event Log listing: Events Since Boot  ----
I 06/29/11 07:48:32 igmp: jrg-vlan: This switch was not elected as Querier
I 06/29/11 07:46:28 ports: port 50 is now on-line
I 06/29/11 07:46:20 igmp: jrg-vlan: Querier Election in process
W 06/29/11 07:46:11 FFI: port 50-Excessive Broadcasts. See help.
W 06/29/11 07:46:11 FFI: port 50-Excessive CRC/alignment errors. See help.
I 06/29/11 07:45:58 ports: port 50 is Blocked by STP
I 06/29/11 07:45:55 ports: port 50 is now off-line
I 06/29/11 07:45:52 ports: port 50 is Blocked by STP
I 06/29/11 07:45:48 ports: port 50 is now off-line
I 06/29/11 07:45:42 ports: port 50 is Blocked by STP
I 06/29/11 07:42:51 ports: port 50 is now off-line
I 06/29/11 07:41:54 ports: port 50 is now on-line
W 06/29/11 07:41:47 FFI: port 50-Excessive Broadcasts. See help.
W 06/29/11 07:41:47 FFI: port 50-Excessive CRC/alignment errors. See help.
I 06/29/11 07:41:25 ports: port 50 is Blocked by STP
I 06/29/11 07:41:21 ports: port 50 is now off-line
I 06/29/11 07:41:20 ports: port 50 is Blocked by STP
I 06/29/11 07:41:13 ports: port 50 is now off-line
I 06/29/11 07:40:13 ports: port 50 is now on-line
I 06/29/11 07:39:44 ports: port 50 is Blocked by STP
I 06/29/11 07:39:40 ports: port 50 is now off-line
I 06/29/11 07:38:21 ports: port 50 is now on-line
W 06/29/11 07:38:06 FFI: port 50-Excessive Broadcasts. See help.
W 06/29/11 07:38:06 FFI: port 50-Excessive CRC/alignment errors. See help.
I 06/29/11 07:37:51 ports: port 50 is Blocked by STP
I 06/29/11 07:37:48 ports: port 50 is now off-line
I 06/29/11 07:37:47 ports: port 50 is Blocked by STP
I 06/29/11 07:37:44 ports: port 50 is now off-line
I 06/29/11 07:37:42 ports: port 50 is Blocked by STP
I 06/29/11 07:37:38 ports: port 50 is now off-line
I 06/29/11 07:37:30 ports: port 50 is Blocked by STP
I 06/29/11 07:37:06 ports: port 50 is now off-line
I 06/29/11 07:36:41 ports: port 50 is now on-line
W 06/29/11 07:36:27 FFI: port 50-Excessive Broadcasts. See help.
W 06/29/11 07:36:27 FFI: port 50-Excessive CRC/alignment errors. See help.

and

I 06/29/11 07:16:45 stp: RSTP Root changed from 0:00260b-666980 to
            61440:000d9d-b11280
I 06/29/11 07:16:34 ports: port 49 is now on-line
W 06/29/11 07:16:25 FFI: port 50-Excessive Broadcasts. See help.
W 06/29/11 07:16:25 FFI: port 50-Excessive CRC/alignment errors. See help.
I 06/29/11 07:16:05 ports: port 49 is Blocked by STP
I 06/29/11 07:16:05 ports: port 50 is now on-line
I 06/29/11 07:16:05 stp: RSTP Root changed from 61440:000d9d-b11280 to
            0:00260b-666980
I 06/29/11 07:16:03 ports: port 50 is Blocked by STP
I 06/29/11 07:16:00 stp: RSTP Root changed from 0:00260b-666980 to
            61440:000d9d-b11280
I 06/29/11 07:16:00 ports: port 50 is now off-line
I 06/29/11 07:15:59 stp: RSTP Root changed from 61440:000d9d-b11280 to
            0:00260b-666980
I 06/29/11 07:15:32 stp: RSTP Root changed from 0:00260b-666980 to
            61440:000d9d-b11280

Why would this swtich, with a priority of 61440 take root when another is upstream and has a priority of 0?  When this swtich is root, it blocks port 50 and everything goes down for a while...until the cisco takes root back.  Id appreciate any help with this.

thanks.

[Richard Brodie_1]

The root switch is on port 50 of this one?

I 06/29/11 07:16:00 stp: RSTP Root changed from 0:00260b-666980 to 61440:000d9d-b11280
I 06/29/11 07:16:00 ports: port 50 is now off-line

What it appears is that the root port has gone down; then the low priority switch has declared itself root. That would be expected behaviour.

I would guess some sort of physical problem with the link.

[Rob Yamry · Accepted solution]

Thanks for your reply.

I went on the Cisco side shortly after I posted this and realized the port has been flapping.  I reseated the gbic and it seems okay so far.... must have gotten bumped somehow.