09-25-2008 02:51 AM - edited 03-06-2019 01:35 AM
I have 15 switches in my LAN.
Two are root.
Here are config and the sh sp
sehqswi04#sh run
!
spanning-tree mode rapid-pvst
spanning-tree extend system-id
!
sehqswi04#sh sp
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32769
Address 0019.304e.7700
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
sehqswi02#sh run
!
spanning-tree mode rapid-pvst
spanning-tree extend system-id
spanning-tree vlan 1-4094 priority 24576
!
sehqswi02#sh sp
VLAN0002
Spanning tree enabled protocol rstp
Root ID Priority 24578
Address 001a.a1cc.b700
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Why isnt sehqswi02 the only root?
Regards Jan
Solved! Go to Solution.
09-26-2008 12:24 PM
Hi
From this description it seems that the Vlan 1 was created in " sehqswi04" before you give "spanning-tree vlan 1-4094 priority 24576" in "sehqswi02" .You might have created the vlan 2 in sehqswi02 after giving the command mentioned above.That may be the reason why sehqswi02 is not the root for both vlan.If you have option to restart sehqswi04, then sehqswi02 will become root for both vlan due to the lower priority value.
Hope this helps.
Ullas
09-25-2008 02:55 AM
switch 1 root for vlan1
and 2 root for vlan 2
this way u distribute the STP load and convergence amonge vlans each vlan has its own STP instances
!!!
if helpful Rate
09-26-2008 03:46 AM
But switch 02 have vlan 1-4064.
spanning-tree vlan 1-4094 priority 24576
So why is switch 04 root for vlan 2?
//Jan
09-25-2008 03:17 AM
Jan
Is 04 switch connected to 02 switch via a trunk link ?
If so then yes 02 should be STP root for vlan 1 as well as the priority of 24576 on 02 for all vlans is better than the 32769 on 04.
Jon
09-26-2008 03:42 AM
Jon,
Yes switch 02 is my backbone switch and have only have trunk ports.
Jan
09-26-2008 03:49 AM
Can you
1) post output of "sh spanning-tree vlan 1" off switch 02.
2) Confirm that you haven't cleared vlan 1 off the trunk link between 02 & 04.
Jon
09-25-2008 04:02 AM
Hi Jan,
If your question is Why sehqswi02 is the root for vlan2 then
the answer is your switch sehqswi02 is configured with the priority of 24578 for VLAN2 in STP instead of 32768 by default.
I think your switch sehqswi04 is having default priority value of 32768 for VLAN2, so that it cant able to Become root for VLAN2.
09-26-2008 12:24 PM
Hi
From this description it seems that the Vlan 1 was created in " sehqswi04" before you give "spanning-tree vlan 1-4094 priority 24576" in "sehqswi02" .You might have created the vlan 2 in sehqswi02 after giving the command mentioned above.That may be the reason why sehqswi02 is not the root for both vlan.If you have option to restart sehqswi04, then sehqswi02 will become root for both vlan due to the lower priority value.
Hope this helps.
Ullas
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: