Saturday, June 1, 2013

Getting unsupported GBICs to work on a cisco switch

Ever had any error while installing a non Cisco GBIC in a switch, i'm pretty sure you have. Cisco is very twitchy when it comes to compatibility with other vendors; like Juniper for instance, that can detect and operate on a pure Cisco SFP or GBIC.

%GBIC_SECURITY_CRYPT-4-VN_DATA_CRC_ERROR: GBIC in port Gi0/1 has bad crc
%PM-4-ERR_DISABLE: gbic-invalid error detected on Gi0/1, putting Gi0/1 in err-disable state

The above error is generated when you insert a non-Cisco GBIC into a Cisco switch. After the switch detect the unsupported GBIC, it puts the interface in an error-disabled mode so that it can protect it self from errors, malfunctions and so on.

The idea is most GBICs have almost the same architecture, and are supposed to work on almost all Vendors, but sometimes the IOS may not support that piece of hardware; a more recent IOS version might. but in any cases, here's how to make it work using these hidden commands

service unsupported-transceiver
no errdisable detect cause gbic-invalid

They run in the global configuration mode. As the commands imply, the first is to tell IOS to ignore the fact that the GBIC is not supported and the second command is to prevent IOS from putting the interface in Err-Disabled mode.

Just make sure you don't use these commands on a production box, because it will teardown your warranty..