If you’re setting up a Cisco Catalyst switch, such as 2960G, 2960X, 3560G, 3560X, 3750G, 4507R-E, etc…, and you insert a non-Cisco branded SFP into one of the SFP slots you will likely receive one of the errors below:
%PHY-4-UNSUPPORTED_TRANSCEIVER: Unsupported transceiver found in Gi0/48 %GBIC_SECURITY_CRYPT-4-VN_DATA_CRC_ERROR: GBIC in port Gi0/48 has bad crc %PM-4-ERR_DISABLE: gbic-invalid error detected on Gi0/1, putting Gi0/48 in err-disable state
This is because Cisco doesn’t support 3rd party SFP or GBIC modules. By support I mean they won’t help you out if you open a TAC case that has anything to do with connectivity to or from your 3rd party SFP.
Now that doesn’t mean it won’t work. We can actually force most Cisco Catalyst switches to accept the SFP with a few short commands starting from 12.2(25)SE.
Why would anyone want to use non-Cisco SFP modules? Mostly cost savings. When you can get 20 multi mode fiber SFP modules from a brand like Ubiquiti for the cost of one Cisco SFP it’s hard not to consider it, especially if you’re a smaller shop (or a large shop that only keeps Smartnet on a handful of devices to maintain software support).
How to Force a Cisco Switch to Accept 3rd Party SFP
When the switch detects an invalid SFP it will errdisable the port. The first thing we need to do is tell the switch not to do this using the undocumented command:
TEST2960(config)# no errdisable detect cause gbic-invalid
The next command we need to run literally tells the switch to service the unsupported transceiver, which is also an undocumented command (means you won’t be able to find it by typing ? or tabbing to auto-complete).
TEST2960(config)# service unsupported-transceiver
Which will result in the following warning output:
Warning: When Cisco determines that a fault or defect can be traced to the use of third-party transceivers installed by a customer or reseller, then, at Cisco's discretion, Cisco may withhold support under warranty or a Cisco support program. In the course of providing support for a Cisco networking product Cisco may require that the end user install Cisco transceivers if Cisco determines that removing third-party parts will assist Cisco in diagnosing the cause of a support issue.
Provided you understand that running a 3rd party SFP may interfere with getting TAC help in the future you can safely ignore the warning. It’s the switch’s last ditch effort to talk you out of using a non-cisco SFP or GBIC.
If you do a ‘show int status‘ you may find that the Type column lists the SFP as Unknown, however it will still work as expected.
Note: I’ve discovered the Catalyst 1000 series switches, such as the C1000-8p and C1000-16p, don’t accept this command. I have been forced to use either legit Cisco brand SFPs or SFPs coded to mimic Cisco SFPs (such as these from FS.com).
Drawbacks of Using Non-Cisco SFPs
As mentioned earlier, if you use a 3rd party SFP you may run into problems if you open a TAC case on an issue that involves the SFP module. TAC may require that you replace the SFP module with a Cisco one before they begin any troubleshooting.
If your switching gear doesn’t have a current SMARTNet contract then I wouldn’t hesitate to run a cheaper (in price) SFP. In my experience, they all work equally good these days, especially the Ubiquiti one’s mentioned earlier.
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