Migration of access layer switches to new VSS core with no downtime

[memcats]

I am migrating 35 closets with dual uplinks to a new VSS 6880 core. I have port channel configured on the VSS core for each closet, and I have configured port channel on the access layer switches with no interfaces assigned to port channel. Interfaces are assigned to the port channel on the VSS core. How do I go about moving these closets to the new VSS with no down time. I have migrated to RSTP ahead of time. I have attached a diagram of what I am referring to.

Thanks

[balaji.bandi]

is your Access layer - Layer 2 or Layer 3 with IGP?

can you update the diagram of how your 1 or 2 Access switch connected in the diagram, they connected to 4510 or 6509?

Hope all the VLAN in place on the new VSS and the same VLAN allowed in the PO between old and new cores?

[memcats]

Access layer switches are layer two. The plan is to get all of the closets moved over and continue to let the old core do the layer three until the night we cut over to layer three on the new VSS core. SVIs have been configured on the new VSS core and they are shut down, and the vlans allowed are the same as they were on the trunks on the old core.

[memcats]

The 4510 is the access layer switch that is currently connected to the 6509, I want to migrate the 4510 to the 6880 VSS core without impacting service as these switches are live in a production environment.

[balaji.bandi]

There is nothing called no downtime here, but STP convergency will take place (depends on what STP you using, if this is Rapid STP, it will be quicker), i am sure the user will not notice, but you sure see 1 to 3 ping loss, which is acceptable in the industry.

i personally do below :

1. Cat 4K any way Blocking port already blocked, so I move to on leg new VSS Active node. ( by creating port-channel on new VSS)

2. Once the Link comes up go into Blocking mode. (this time should be very cautious.  (if you want to you can don controlled VLAN allowed here) to verify the results.

3. once the link comes up allow the VLAN required some at a time, or 1 at a time based on the network and critical vlans.

4.  then shutdown the port connected to the OLD core, it should quickest convergency new port go unblock start forwarding the traffic, ( so to be safe, this where you call checkpoint of testing).

Once the above steps are good and all working as expected.

5, move the other link and connect to VSS part of port-channel and bring no shutdown the port.

This is the high-level approach.

make sense?

[Reza Sharifi]

Are you planning to move over all the SVIs with the same IPs or use new SVIs and new IPs? If yes, how many vlans do you have?

Are you using HSRP or VRRP on the existing core switches?

Do the access switches have extra (2) uplinks or you have to move over the once connected to the existing core switches?

Although you can do a whole lot of planning, design, and documentation ahead of time to make sure you have the shortest possible window, this type of migration is usually not without downtime. So, you do need a maintenance window.

HTH

[memcats]

Hello Reza,

The SVIs are on the new core shut down, will no shut them when we do the layer three cut over.

Old Core are using HSRP

Closets have dual uplinks to the old core

[Reza Sharifi]

Hi,

Closets have dual uplinks to the old core

So, you have extra available ports that can be used for the new core?

The reason I ask is if you have 2 extra ports on the access switches, you can connect the cables and build the Portchannels ahead of time and keep them down until the maintenance window, you can then simply no shut the Portchannels and bring them up. It saves you time.

HTH

[memcats]

No we don't have extra available port to use. We only have the two uplinks that are currently connected to the 6509, which we will have to move to the VSS core.

.

[Reza Sharifi]

Ok, then during the maintenance window, you would have to move these ports to the new core switches and add them to the Portchannels.

HTH

[memcats]

Ok, I think I see it now. I would move the blocked port on the access layer switch to the new VSS core and then move the forwarding port to the new core, RSTP will converge quickly. Then I need to add the access uplink to port channel to form a etherchannel with the VSS ports.

[balaji.bandi]

that is the best approach I see based on your information provided, and my past reply to your inputs.