Bypassing Cisco’s Protection on “Unsupported” SFPs

Well dear homelabber, you’re on a budget. You have some old Cisco 2960s you bought off ebay. You also found some cheap fiber transceivers that are not Cisco name brand. Perhaps you have some that you bought from Ubiquiti and they work fine. You plug them into your Cisco switch and… there’s no link! You check your console messages and you see:

LABISPSW#Apr 13 17:20:12.147: %PHY-4-SFP_NOT_SUPPORTED: The SFP in Gi0/11 is not supportedApr 13 17:20:12.147: %PM-4-ERR_DISABLE: gbic-invalid error detected on Gi0/11, putting Gi0/11 in err-disable stateLABISPSW#Apr 13 17:20:12.147: %PHY-5-TRANSCEIVERINSERTED: Slot=1 Port=11: Transceiver has been inserted

Ugh! You may have even seen the laser light up or even the port start trying to negotiate and then she’s dead!

Bypassing Cisco’s protections

Obviously, Cisco prefers Cisco-branded SFPs. The thing about Cisco-branded SPFs are that they cost ????. So to use your non-kosher SFPs, enter config mode and enter the following commands:

service internalno errdisable detect cause gbic-invalidservice unsupported-transceiver

Once you press enter on that last command, you’re going to get the following warning:

 Warning: When Cisco determines that a fault or defect can be traced tothe use of third-party transceivers installed by a customer or reseller,then, at Cisco's discretion, Cisco may withhold support under warranty ora Cisco support program. In the course of providing support for a Cisconetworking product Cisco may require that the end user install Ciscotransceivers if Cisco determines that removing third-party parts willassist Cisco in diagnosing the cause of a support issue.

You may also notice if you use the help command on service, you won’t see “unsupported-transceiver” and it won’t tab complete for you either. That’s because in business, Cisco doesn’t want you to know that command is there or what it does.

In your home lab, more power to you!

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