I just added a new stack of 3750 switches to my network. The stack is running of a 6509. Everything seems to be working fine. However I keep getting the following messages in the Syslog
Nov 27 16:27:05 itg-exchsw-dub 4887: 004851: *Mar 6 06:08:20: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 151: New Root Port is GigabitEthernet2/0/1. New Root Mac Address is 0007.b38c.d496 Nov 27 16:27:05 itg-exchsw-dub 4888: *Mar 6 06:08:20: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 151: New Root Port is GigabitEthernet1/0/1. New Root Mac Address is 0007.b38c.d496 (itge-exchsw-dub-1) Nov 27 16:27:07 itg-exchsw-dub 4889: *Mar 6 06:08:21: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 150: New Root Port is GigabitEthernet1/0/1. New Root Mac Address is 0007.b38c.d495 (itge-exchsw-dub-1) Nov 27 16:27:26 itg-exchsw-dub 4890: 004852: *Mar 6 06:08:41: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 151: New Root Port is GigabitEthernet2/0/1. New Root Mac Address is 0007.b38c.d496 Nov 27 16:27:28 itg-exchsw-dub 4891: *Mar 6 06:08:42: %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 150: New Root Port is GigabitEthernet1/0/1. New Root Mac Address is 0007.b38c.d495 (itge-exchsw-dub-1)
This keeps happening. Is the spanning tree unstable?
I believe before you added your stack to Cat6509 , Cat6k was your root switch and now new siwtch is taking a place as a root switch because may be your stacked 3750 switch mac address is lower compared to Cat6k switch.
I will suggest you to always hardcore your root switch in your network so that any new switch cannot attemt to become a root switch with spanning tree root command.
spanning-tree vlan vlan_ID root
The 6509 is running in Hybrid mode. If I check show spantree on the CatOS it shows me that all ports are forwarding. Whereas the 3750 has one port blocking. The root of the tree will have all its ports in a forwarding state, am I right? So therefore the 3750 must not be the root.
If I want to set the 6509 CatOS to be the root for all vlans what command do I run?
set spantree root [secondary] [vlans] [dia network_diameter] [hello hello_time]
Yes the root switch will always have all the ports into fwding state.
Error Message SPANTREE-5-ROOTCHANGE: Root Changed for [chars] [dec]: New Root Port
is [chars]. New Root Mac Address is [enet].
Explanation This message means that the root switch changed for a spanning-tree instance. The first [chars] and [dec] is the interface ID for the previous root port, the second [chars] is the interface ID for the new root port, and [enet] is the Ethernet address of the new root port.
Looking at the log it seems like your one of the port is flapping and that's why STP is learining the root for vlan 150 and vlan 151 from a different port. Check if you have any link going up/down.
Check show log on the switch. Let us know the Connectivity on the network.
I Have checked the logs and monitored the interface status. No links are flapping. The trunk ports are in a steady state. The stack cable is good and everything looks fine!!
Thats why I can't get to the bottom of the problem! :(
Can you confirm this mac address 0007.b38c.d496 belongs to which device and I believe its only happeneing for vlan 151.
Can you confirm if there is any non default configuration of spanning tree on any of the switch especially on stacked 3750 and cat6509?
You are hitting a bug CSCeb78548. This is a cosmetic issue.
Externally found moderate defect: Resolved (R)
Cat OS may incorrectly log STP root change: SPANTREE-5-ROOTCHANGE
Any Catalyst OS box may incorrectly report an STP root change with the following message:
%SPANTREE-5-ROOTCHANGE:Root changed for Vlan Y: New root port n/m. New Root mac address is
This is caused by it not verifying the old root so it may log a root change even if the topology change results in the same switch being root. This was introduced due to the fix for CSCdz04679.
A catalyst running CatOS incorrectly report an STP root change with the following message:
2003 Jun 09 11:42:28 EST -04:00 %SPANTREE-5-ROOTCHANGE:Root changed for Vlan
Y: New root port n/m.
New Root mac address is XX-XX-XX-XX-XX-XX.
This is just cosmetic, and should not affect the operation of the switch
Change logging level on the SPANTREE facility down to 4.
This enhancement was introduced via a bug
CSCdz04679 where user wanted to see a syslog whenever spantree root is changed for any vlan or instance.
The original fix also used to generate a syslog when there is a root port change and not the actual root change. This was introduced in 5.5(19) , 6.4(3), 7.6(3).
New syslog is ROOTCHANGE at spantree logging level 5.
Later it has been found that switch was generating Rootchange syslog even when there is no root change or root port change. This has been fixed in 5.5(20), 6.4(7), 7.6(5), 8.2(1).
Now the syslog is generated only when there is actual root change. If there is root port change but no root change then this syslog is not generated.
1. Lower the spantree logging level to 4.
HTH,Please rate if it does.