Turn Off Spanning-Tree on HWIC-4ESW

Unanswered Question
Apr 1st, 2010

I have a customer whose routers and WAN we provide and maintain.  There are twenty 2821 routers each with a 4-port HWIC-ESW module in them.   We provide the customer with Metro Ethernet for Data and VoIP between their sites.   The 2821 routers connect to a  Cisco ME 3400 switch that is our MetroEthernet DeMarc.  We have an interface on the 4 port switc module interface configured as an access port, and connected to a UNI port on the ME 3400 Metro Switch.   VTP, STP, CDP is tunnelled across the Carrier network to all the other customer branch locations.

This has been working very well for nearly two years until recently.   Our Metro Ethernet engineers have started upgrading the software images on the core MetroEthernet Switches, and the customer has now been having  a spanning tree blocked port issue on whichever 4-port switch module is configured as the root bridge of the Metro Wan set up for the customer.   The root bridge's interface to the ME WAN goes into blocked status until a shut/no shut of the interface brings it back to forwarding.   The upgrades are done at night on the carrier network, and we get notices about when they are performed. 

We have correlated the times of the carrier network upgrades to the times of the spanning-tree blocked issue.   It affects only which switch module is root. all others un-affectd.

I was wondering if there would be any problems of disabling spanning-tree on the switch module of each branch router.   There only connection is to the ME 3400 switch that is connecting it to the ME WAN for the customer.   All other branches connect in this manner.

The switch module does not connect to anything else.

Anyone have any thoughts?

I have this problem too.
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Ganesh Hariharan Thu, 04/01/2010 - 10:12

I have a customer whose routers and WAN we provide and maintain.  There are twenty 2821 routers each with a 4-port HWIC-ESW module in them.   We provide the customer with Metro Ethernet for Data and VoIP between their sites.   The 2821 routers connect to a  Cisco ME 3400 switch that is our MetroEthernet DeMarc.  We have an interface on the 4 port switc module interface configured as an access port, and connected to a UNI port on the ME 3400 Metro Switch.   VTP, STP, CDP is tunnelled across the Carrier network to all the other customer branch locations.

This has been working very well for nearly two years until recently.   Our Metro Ethernet engineers have started upgrading the software images on the core MetroEthernet Switches, and the customer has now been having a spanning tree blocked port issue on whichever 4-port switch module is configured as the root bridge of the Metro Wan set up for the customer.   The root bridge's interface to the ME WAN goes into blocked status until a shut/no shut of the interface brings it back to forwarding.   The upgrades are done at night on the carrier network, and we get notices about when they are performed. 

We have correlated the times of the carrier network upgrades to the times of the spanning-tree blocked issue.   It affects only which switch module is root. all others un-affectd.

I was wondering if there would be any problems of disabling spanning-tree on the switch module of each branch router.   There only connection is to the ME 3400 switch that is connecting it to the ME WAN for the customer.   All other branches connect in this manner.

The switch module does not connect to anything else.

Anyone have any thoughts?

Hi,

Genral recommednation never play with algorothm which are in built mechanism of devices and STP is alogorithm which prevents looping at l2 level.so what i would suggest design you STP topology along with the traffic flow and create root bridge with configuration like pirority in STP.

Check out the below link on disabling STP on per vlan basis HWIC-4ESW

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t8/feature/guide/esw_cfg.html#wp1048204

Hope to Help !!

Ganesh.H

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