spanning-tree root question

[katerina.dardoufa]

Hello all,

we have the attached topology (two nexus 5K) on two sites, which are connected via trunk links. On the Nexus we also have connected devices which perform bridging (IPS/Imperva).

When running the "show spanning-tree root" command on any of the devices I get the following for the bridged vlans:

Site-1(1)# sh spanning-tree root

Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- ------- ----- --- --- ----------------

VLAN0040 40 0023.04ee.be0a 0 2 20 15 This bridge is root
VLAN0041 40 0023.04ee.be0a 21000 2 20 15 port-channel1
VLAN0070 70 0023.04ee.be0a 0 2 20 15 This bridge is root
VLAN0071 70 0023.04ee.be0a 21000 2 20 15 port-channel1
VLAN0080 80 0023.04ee.be0a 0 2 20 15 This bridge is root
VLAN0081 80 0023.04ee.be0a 21000 2 20 15 port-channel1
VLAN0090 90 0023.04ee.be0a 0 2 20 15 This bridge is root
VLAN0091 90 0023.04ee.be0a 21000 2 20 15 port-channel1
VLAN0131 131 0023.04ee.be0a 0 2 20 15 This bridge is root
VLAN0132 131 0023.04ee.be0a 21000 2 20 15 port-channel1

Lets say that 70/71 are bridged. Under the Root ID column I only see vlan 70, even when viewing the root for vlan 71. What is this number "70" referring to? Is it normal to see this output when bridging is also in place?

Thanks in advance,

Katerina

[Jaderson Pessoa]

hello

show spanning-root 

VLAN0302 302 700b.4f26.5a80 0 2 20 15

show spanning vlan 302

Bridge ID Priority 302 (priority 0 sys-id-ext 302)

this information is "sys-id-ext 302"

that is used to root election process in case of the same numbers in whole process.

[katerina.dardoufa]

Ok! Got it! I have never noticed it before and since the vlans in question are bridged it makes sense.

Thanks!

[Jaderson Pessoa · Accepted solution]

Great... mark as solved if possible, it will be used to an other cases.