Determining What Kind of SFP Is Installed in a Cisco Switch

There are several round about ways of determining what kind of SFP is installed in a socket on a Cisco switch, but I think the easiest is this:


testswitch#show int gi3/1/2 capabilities
GigabitEthernet5/1/1
  Model:                 WS-C3750X-48
  Type:                  1000BaseLX SFP
  Speed:                 1000
  Duplex:                full
  Trunk encap. type:     802.1Q,ISL
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: percentage(0-100)
  Flowcontrol:           rx-(off,on,desired),tx-(none)
  Fast Start:            yes
  QoS scheduling:        rx-(not configurable on per port basis),
                         tx-(4q3t) (3t: Two configurable values and one fixed.)
  CoS rewrite:           yes
  ToS rewrite:           yes
  UDLD:                  yes
  Inline power:          no
  SPAN:                  source/destination
  PortSecure:            yes
  Dot1x:                 yes

You can see the type and everything. You'll need to be enable mode, of course.

Using 3rd SFP's on Cisco 3560s and 3750s

It's well known that Cisco does not especially like to support third party hardware products within their switches. Perhaps one of the most common cases of this is the support for 3rd party SFPs on the Catalyst line.

During the day of GBICs, 3rd party interfaces usually worked. Enter the SFP. Here's a typical response from a 3750 when plugging in, say, a Finisar SFP:

Feb  27 00:01:47.952: %GBIC_SECURITY_CRYPT-4-VN_DATA_CRC_ERROR: GBIC in port Gi2/0/1 has bad crc
*Feb 27 00:01:47.952: %PM-4-ERR_DISABLE: gbic-invalid error detected on Gi2/0/1, putting Gi2/0/1 in err-disable state

and a show int status demonstrates this:

show int status | inc Gi
Gi2/0/1                      err-disabled 1            auto   auto unknown

As an unspported work around work around, you can tell the switch to ignore the fact that the SFP was not blessed by Cisco. Keep in mind that Cisco will likely tell you to put in Cisco branded SFPs and that they won't support you with 3rd party SFPs in place (i.e., this is at your own risk!)

from conf t:
service unsupported-transceiver
 no errdisable detect cause gbic-invalid

You'll see this message


 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.

If you then move the SFP to another port, you should see something like this in int staus:

Gi2/0/2                      connected    1          a-full a-1000 unsupported

It works... don't forget to do a write mem.