Hello cisco experts!
I've got some problems with STP at network due to migration from old non-cisco network switches to cisco switches.
It's not an issue while I keep network loopfree. I'm migrating from old network. But at some moment I had to turn off spanning tree and core switch.
Simplified network topology:
old network ----- 3com ---access_ports ------ nexus7010 --- trunk ---- 2960S_stack.
At 3com stp turned off. 3com is end of sale, end of life and end of support for a long time ago, no specialists left and it has some problems, so trying to use features at 3com results unexpected problems with switch. So I can't touch 3com configuration.
New network with nexus and 2960S stacks are stp aware - rapid-pvst.
Nexus and 3com connected via access port vlan 10 (this is beacuse nexus and this old 3com did not want to make trunk, other newer 3com's made trunks successfuly with nexus).
At nexus7010 I had to turn off STP at one moment.
After that 2960S stacks became not working - second switch in stack has all ports orange color and in logs I saw stp battle:
23392024: 15154930: Mar 12 13:49:16: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 10 (2960S-1stfloor-stack)
23392025: Mar 12 13:49:17: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 10: New Root Port is StackPort1. New Root Mac Address is 0012.a9fd.xxxx
23392026: 15154931: Mar 12 13:49:17: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 10: New Root Port is GigabitEthernet2/0/48. New Root Mac Address is 0012.a9fd.xxxx (2960S-1stfloor-stack)
23392027: 15154932: Mar 12 13:49:18: %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 10 (2960S-1stfloor-stack)
23392028: Mar 12 13:49:18: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 10: New Root Port is StackPort1. New Root Mac Address is a456.3092.xxxx
23392029: 15154933: Mar 12 13:49:18: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 10: New Root Port is GigabitEthernet2/0/48. New Root Mac Address is 0012.a9fd.xxxx (2960S-1stfloor-stack)
Why that happens?
What message "Root Changed for vlan 10: New Root Port is StackPort1" means? And in what situations it may happen?
I see stp battle and switch changes stp root frequently for vlan 10 - this root appears:
- this switch is root
- another switch with lower mac (another 2960S_stack)
- different 3com switches from old network cloud.
1) Why stp changes frequently and not stabilize after time? It should know about one root and stop changing it. Is not it?
2) Why all stack members exept master not working and how this is correlates to stp problems at network?
Thanks in advance!
