Unsupported SFPs in Cisco Switches – a warning!

So… an SFP has blown and there are no spare Cisco ones around. As luck would have it you’ve found a one made by HP, or some other manufacturer and tried installing it, only to see in the logs that there is an “Unsupported transceiver found in GiX/X” (or something similar.)

Damn.

A  bit of googling shows you that this is easily worked around with the following commands. The first of these is a hidden command and must be typed in full:

# service unsupported-transceiver
# no errdisable detect cause gbic-invalid

What you aren’t told, however, is that the first command behaves differently across the various Cisco platforms! On most kit, it’ll happily take the command, give you a warning about support (on your head be it) and then your SFP will spring into life. On others, such as the 4900M, for example, it will take down and reinitialise all of your X2 modules and SFPs.

This kind of outage is probably not what you want during the day, so unless your switch is isolated anyway, it’s probably best to schedule this out of hours if you can’t lab it first to find out what the consequences will be.