We had an interesting issue last week while replacing a Cisco Catalyst 4510R with a Juniper EX4300 Stack. The second switch in the Virtual Chassis stack appeared to have a bad PoE controller since none of the PoE ports on that switch were working. So we had to replace the switch with a spare.

First we had to upgrade the JunOS code on the switch to match the software on the existing stack. After we downgraded the software we powered off the switch, connected the stacking cables or VCP ports then powered the switch back on… it was initially detected as the 4th switch in the virtual chassis stack. Next all we did was replace the serial-number for switch 1 with the new switch (switch 4) and commit.

{master:0}[edit]
root@TEST-SW01# set virtual-chassis member 1 serial-number PD37XXXXXXX

{master:0}[edit]
root@TEST-SW01# commit
configuration check succeeds
fpc2:
commit complete
fpc3:
commit complete
commit complete

That was all I needed to do. After the commit everything started working on the replaced switch. I eventually rebooted the stack just to be sure nothing broke or stopped working but everything was fine.

If you read through the JunOS libraries, you’ll find a very drawn out process documented here.

Is all that really required?
Deleting the member, and then reprogramming the switch?

Any Juniper switching gods here to confirm or deny?

Cheers!