when doing command "no spanning-tree vlan 1 etc.

[davidfranek]

All,

When performing command no spanning-tree vlan ? ? to remove or disable spanning-tree for a particular vlan, how do you add it back to be enabled.

When trying to add Example, spanning-tree vlan 1-901 it only adds a few back. These commands are still present.

no spanning-tree 155-156,160-165,167-179,etc.

[Peter Paluch · Accepted solution]

Hello David,

The command you are using to activate the STP back on selected VLANs is correct. What is the switch platform and IOS version that exhibits this symptom? Also, does anything change if you try to enable STP for a particular single VLAN using the command spanning-tree vlan 155, for example? When performing these experiments, does the VLAN 155 exist?

I haven't yet seen a similar problem, to be honest.

Best regards,

Peter

[davidfranek]

This particular environment is a remote site that still uses 3550,3560 and 3560-x. I see the 3550 has a Platform limit of 128 STP instances exceeded. Most of the vlans are not present or used within the remote site. I will focus on vlan used at the site.

[davidfranek]

All of the switches use the latest avaliable IOS for LAN base.

[Peter Paluch · Accepted solution]

David,

I am a little confused. Did this occur on several switches and different platforms, or are we debugging this problem on a single switch only? If only a single switch is affected, can you post its (sanitized) configuration here along with the show spanning-tree summary and show vtp status?

Best regards,

Peter

[davidfranek]

Sorry for the confusion. I have a remote site with 3350 and 3560 switches. I needed to re add spanning-tree vlans after someone disabled them. Some of the 3350's had a platform limit because of IOS enterprise version. The other vlans were not removed because they were not used.

Thanks, for all the replies

[Peter Paluch]

David,

Thank you for the generous ratings.

One recommendation: you seem to run a lot of VLANs on the remote site. I would strongly recommend considering using the MSTP. Usually, the maximum number of STP instances is lower than the maximum number of VLANs on a platform - for example, on 2960 Catalyst switches, the maximum number of STP instances is 128 while the maximum number of VLANs is 255. Having more than 128 VLANs on 2960 could therefore induce switching loops into the network for those VLANs which are unable to obtain a STP instance. You may well be running into similar issues. Besides, the need to maintain 128 unique STP instances with all the details around (BPDUs, timers, roots, etc.) can be quite CPU intensive, and does not really make much sense - most of these STP instances create the same spanning tree.

The MSTP would alleviate these issues. It runs a couple of instances (you define how many), and the VLANs share these instances (you define which VLANs are shared to which MSTP instance). Regardless of how many instances and VLANs exist, only a single BDPU is sent every hello_time and thus, singnificantly less data and state information has to be transmitted and cared about. Transitioning to MSTP and configuring it requires some skills but in an afterwards stable network, it will repay itself.

Give it a thought

Best regards,

Peter