Bought a cheap 3550 (well, cheap is relative - layer 2 only - WS-C3550-24-SMI), put a host name, IP address, and snmp community names on it and plugged it in to replace a much older 2900.
Spanning tree went nuts and set the fiber gig port I used to blocking mode. There is no way for a duplicate connection to exist - only have one pair of multmode fiber trenched between buildings as a connection back to the server room.
The errors were:
00:37:16: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
00:37:18: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
00:37:18: %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk GigabitEthernet0/1 VLAN1.
00:37:18: %SPANTREE-7-BLOCK_PORT_TYPE: Blocking GigabitEthernet0/1 on VLAN0001. Inconsistent port type.
00:37:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
00:37:35: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
which repeated until I shut the port.
This box is connected to a Catalyst 4900 (WS-C4912) with all fiber ports. Nothing fancy set up on it either. Mostly factory defaults except for minimal changes for management.
To finaly get things to settle down, I turned off trunking on the 4900 port connecting to the 3550 (set trunk 2/6 off dot1q 1-1005). All ports were set to auto, which should have prevented any attempt at trunking.
Any idea why the 3550 and 4900 switch plugged together over one multimode fiber connection should have a problem? The fiber has been working just fine for several years. I only moved the GBIC, diden't even unplug the fiber.
Are there new secrets to setting up a 3550 out of the box? Or, did my changes only keep me occupied and not really have anything to do with the errors?
My Cisco rep suggested turning on UDLD which I did on the 3550, but the 4900 does not support it. Did not help anyway.
Any suggestions are greatly appreciated.
