Question on 'strange' STP behavior

news2010a · ‎12-14-2009

Hi, can you help answer this question. This is a continuation from another thread. Please see attached diagram for details.

Imagine I attempt to change 2950C from vlan 22 to vlan 7. I created the vlan 7 database on 2950C, then the SVI int vlan 7 and assigned correct IP. I configured the default-gateway to vlan 7 and assigned 'int range f0/1 - 22' to access vlan 7 - OK. Then I deleted all vlan 22 information from 2950C. From the network I was able to ping SVI vlan 7 OK.

Twenty minutes later people complained that servers pointing to other switches on vlan 7 stopped responding.

Question:

Based on the mac address for 2950A and 2950C, I believe that 2950A should remain as the root bridge for vlan 7. Even though the ip default-gateway is not set on 2950A, in theory I think this is not enough to explain why when I made changes on 2950C to vlan 7 servers on vlan 7 stopped working.

Note: I am aware the 4507 should be setup as the STP root.This network as is now is suboptimal. At this point I just want to make sure I can justify why trying to make 2950C as a vlan 7 configuration did not work.

sridsdale · ‎12-14-2009

Looking at the Visio the trunks from the 2950C to the 4507s was only allowing VLAN 22. You don't mention changing this when you added VLAN 7 to the switch. Did you allow VLAN 7 on the trunk at both ends?

news2010a · ‎12-14-2009

Yes, I adjusted trunks on both ends accordingly to vlan 7.

Giuseppe Larosa · ‎12-15-2009

Hello Marlon,

I think it would have been better to go on using the previous thread.

you can use the next link on bottom right to go to older threads ( next = older it may look like strange I know)

Best Regards

Giuseppe

news2010a · ‎12-15-2009

Sorry Giuslar. In fact I attempted to search the other thread, but I didn't find it (in the past I used to find my posts easily by doing a search. On this new imrproved website that search feature returns different results. I will play a little more today).

Regards,