Can adding VLANs to a VPC be done hot?
In this scenario, we have a VPC '17', consisting of two single port port-channels 'po17'. There are 2 x N5K's (5548s) - so po17 from both sides combine to create the VPC.
The downstream devices are blade switches (Cisco 3020s). We want to add a new VLAN to one side, then the other without loss of connectivity for the VMs behind the 3020s. Downstream can handle this because if one side fails, the other side picks back up.
I know if one of the Port-Channels in the VPC goes down we still stay up, but since we're adding a new VLAN to one of the VPC member Port-Channel, the VPC will loose consistency and I didn't know if that would cause a problem.
While it is certainly a good idea that a VPC has the same allowed VLAN list on all sides, it is not a requirement. Take a look at the output of "show vpc consistency-parameters global".
switch# show vpc consistency-parameters global Legend: Type 1 : vPC will be suspended in case of mismatch Name Type Local Value Peer Value ------------- ---- ---------------------- ----------------------- QoS 2 ([], [3], [], [], [], ([], [3], [], [], [], []) []) Network QoS (MTU) 2 (1538, 2240, 0, 0, 0, (1538, 2240, 0, 0, 0, 0) 0) Network Qos (Pause) 2 (T, F, F, F, F, F) (T, F, F, F, F, F) Input Queuing (Bandwidth) 2 (50, 50, 0, 0, 0, 0) (50, 50, 0, 0, 0, 0) Input Queuing (Absolute 2 (F, F, F, F, F, F) (F, F, F, F, F, F) Priority) Output Queuing (Bandwidth) 2 (50, 50, 0, 0, 0, 0) (50, 50, 0, 0, 0, 0) Output Queuing (Absolute 2 (F, F, F, F, F, F) (F, F, F, F, F, F) Priority) STP Mode 1 MST MST STP Disabled 1 None None STP MST Region Name 1 "" "" STP MST Region Revision 1 0 0 STP MST Region Instance to 1 VLAN Mapping STP Loopguard 1 Disabled Disabled STP Bridge Assurance 1 Enabled Enabled STP Port Type, Edge 1 Normal, Enabled, Normal, Enabled, BPDUFilter, Edge BPDUGuard Disabled Disabled STP MST Simulate PVST 1 Enabled Enabled Allowed VLANs - 1,10,100-101,200-201 1,10,100-101,200-201,2 000 Local suspended VLANs - - -Type 1 parameters absolutely MUST match, else the vPC will be suspended. "Allowed VLANs" is neither a Type 1 or Type 2 parameter.
You should be able to modify the allowed VLAN list without problems, but obviously try to keep things consistent regardless, otherwise you'll still have issues, even though the vPC doesn't get suspended.
EDIT: You probably already know this but just to be sure - include the peer-link in your VLAN changes, as the VLAN (not the entire vPC) will show up as "suspended" on all vPCs until you do.
Hey Mierdin, thanks a ton - especially the reminder about the peer link, I hadn't even thought about that! I feel confident moving ahead with your explanation.
As a side note you will get a log message to say that forwarding has been suspended on VLANX as its not added on the peer link. Asaide from that there is absolutely no issue with adding VLAN's while 'hot', we do it all day long.
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Content dated before 7/24/2021 11:53 AM
A L 8 years ago
Hey Mierdin, thanks a ton - especially the reminder about the peer link, I hadn't even thought about that! I feel confident moving ahead with your explanation.