VLAN Mapping (VLAN Translation) impact on Spanning-Tree

j.a.m.e.s · ‎08-21-2018

All,

I would like to map VLAN 10 on one switch-pair to VLAN 11 on another switch-pair. The planned config is as follows:

Sw01 #
interface Port-channel11
 switchport
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 799
 switchport trunk allowed vlan 10,11
 switchport mode trunk
 switchport nonegotiate
 switchport vlan mapping enable
 switchport vlan mapping 10   11
 mtu 9216
 mls qos trust dscp
exit

As you can see there is potentially a loop, but we have configured rapid-pvst everywhere. Could anyone advise on the impact of VLAN-Translation on spanning-tree please?

paul driver · ‎08-21-2018

Hello

Whats your reasoning to do this?

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Kind Regards
Paul

j.a.m.e.s · ‎08-21-2018

I'd like to migrate servers gradually to a new switch and use a new VLAN id on the new switch.

Reza Sharifi · ‎08-21-2018

Hi,

So, you are trying to move the servers to a new switch, a new vlan (11) and keep the servers in the same IP segment they are now without downtime?

j.a.m.e.s · ‎08-21-2018

Yes, that's right. I understand that eventually the L3 SVI will have to be migrated to the new switch and at this point we'll need a maintenance window.

j.a.m.e.s · ‎09-03-2018

I think the answer is that the VLAN mapping will break PVST so my intended outcome isn't possible and would cause an L2 loop if configured. Changing the VLAN ID before/after the migration would be the way to go.

There is some mention of using MST in the NX-OS Switching Configuration guide (see "VLAN Translation"), so this might be a possibility to consider on a future occasion.

Regards

James.