OSPF drop due to L2 port leaving bridge port

[phil_carter]

Hello,

I have seen a hit to our network caused due to the below message:

2006 Nov 28 01:03:54 %ETHC-5-PORTFROMSTP:Port 8/4 left bridge port 8/4

2006 Nov 28 01:04:09 %ETHC-5-PORTTOSTP:Port 8/4 joined bridge port 8/4

This connects a 6500 (with layer-3 MSFC card) switchport to a Layer-3 7507 router FastEthernet interface. OSPF adjacency was lost across this connection due to the error above.

However, output interpretor suggests "Recommended Action: No action is necessary. This message is provided for information only". The total loged outage was for 15secs.

The physical interface did not drop, and nothing was seen in the logs of the 7507 router. Has anyone seen this before or can advise why this happened?

Rgds

Phil

[amit-singh]

Hi Phil,

Which CatOS you are running. This could be some cosmetic issue with in the code as well as I have seen it on many codes. Try the following on the interface connecting to 7507.

SET SPANTREE PORTFAST ENABLE

SET TRUNK OFF

SET PORT CHANNEL OFF

But you OSPF adjacency should not be lost even if the outage was for 15 secs, if you are on default timers. What are the OSPF timers you are using?

HTH,

-amit singh

[phil_carter]

Hi,

CATOS Code: cat6000-sup2k8.8-5-2.bin

config on port 8/4 facing 7507:

set vlan 401 8/4

set port speed 8/4 100

set port duplex 8/4 full

clear trunk 8/4 1006-1023

set trunk 8/4 auto negotiate 1-1005,1024-4094

HAVC6502> (enable) sh port 8

* = Configured MAC Address

# = 802.1X Authenticated Port Name.

Port Name Status Vlan Duplex Speed Type

----- -------------------- ---------- ---------- ------ ----------- ------------

8/4 HAVR703 FA3/0/0 connected 401 full 100 10/100BaseTX

Noticed this is configured as a trunk and VLAN 401, although the switch sees it as a 401 switchport, not trunk. Should trunking be turned off? spantree portfast enable is also not configured.

What is the impact of configuring portfast and removing trunk status? And what are the benefits? Would this help reduce TCNs in the network?

Spanning-tree is not my favourate protocol and generally requires extreme caution when implementing any change (especially when this is on the core of your network).

rgds

Phil

[phil_carter]

Hi,

BTW: Default OSPF timers in use.

rgds

Phil

[amit-singh]

Hi Phil,

When you enable the portfast on the port it transition the port directly to forwarding state and doenot go thorugh the normal listening and learning state. Hence the port will immediately be in up state. If you switchport is connecting to another switch or bridge it is never suggested to turn the portfast on.The trunking should be set to off.

Just run the commands that were suggested on the port and you should be fine to go with it.

HTH,

-amit singh