Switching

If you have a VC with only EX4300, you can do NSSU, which means that it will fail over between master and backup switch.

In the EX4600 you can do ISSU instead, which means that it will spawn a virtual machine in the same switch and fail over between.

Using these two techniques, how do you uppgrade a mixed EX4300/EX4600 VC? Can you only do NSSU then?

And when we are talking about VC, can someone explain why you would not want all switches in a VC to potentially becoma master/backup? If configuring them in linecard role they can never assume master/backup. Why would you now want as much redundancy as possible? 

Regarding the mix of EX4600 and EX4300 in a VC, NSSU will be performed.

The advantage of preprovisioned mode is that you can control which devices can become RE/BK.

Not using preprovisioned mode can lead to unexpected results in term which FPCs are the RE/BK and their assigned FPC numbers.

Yes, you are right that if the two FPC acting as RE/BK in a preprovisoned mode fails, you will have a headless VC. This can be solved by letting any other FPC become one of the RE/BK.

However, it's unlikely that from a stack, you will have outage only for RE/BK. If those two fails in the same time, then probably the outage is big and probably the other FPCs went down.

On the other note, if only the RE goes down, it is expected to quickly check what happened with it and replace it. Nobody should run with a single RE.

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Thanks for a great reply!

However I am still not sure what the unexpected could be regarding some switch taking over as RE.

I can however think of one small reason.

Say not all MGMT interfaces are patched, then it would not be too good if a switch which not have had their MGMT interface connection to assume master, since it would mean it cannot be managed over IP any longer.

That should work as well. Your next-hop(ARP) for vme.0 IP address will the MAC from vme interface. If another FPC(that is not the master) will get the packets, they will be redirected to the RE(using internal connectivity, aka vcp ports).

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