When we're doing support for clients, or recommending cost-cutting measures for upgrading their networks, one problem we often run into involves the Cisco Catalyst line of switches, and using a Cisco compatible SFP with them.
The Small Form-factor Pluggable (SFP) transceiver is an absolutely standardized technology, which allow Gigabit optical ports to host a variety of other connections. Its hot-swapability means that it's simple to change the configuration of your switch or router, with minimal upgrade costs.
Theoretically, any Cisco compatible SFP should be able to work in any network hardware. Unfortunately, some people run into issues using third-party SFPs with the Cisco Catalyst Line.
Getting Non Cisco SFPs To Work In Cisco Catalyst Switches
In most cases, if you plug an SFP from anyone but Cisco into a Catalyst, you get an error message that looks something like:
%PHY-4-UNSUPPORTED_TRANSCEIVER: Unsupported transceiver found in Gi1/0/0
%GBIC_SECURITY_CRYPT-4-VN_DATA_CRC_ERROR: GBIC in port 65538 has bad crc
Why does that happen? Well, within every SFP is a small chip containing a range of information about the device, including its Vendor Name, serial number, and CRC. When it's first plugged into a Catalyst's SFP port, the Catalyst queries this chip for its credentials.
If it's not Cisco, the Catalyst automatically shuts the port down entirely.
It's somewhat underhanded, but since SFPs aren't overseen by a central standards body -unlike WiFi, for example- there's no one around to tell Cisco not to do it. This can ultimately lead to needlessly expensive upgrades when third-party SFPs truly can work just as well in all Cisco Catalyst switches.
You just need to go into the IOS control panel and enter in two commands at the hash prompt. First:
# service unsupported-transceiver
This command is totally undocumented, and won't even show up in the usual help files. It does exactly what it sounds like.
The Catalyst will throw an error up at this point, saying (in essence) that using third-party SFPs could lead to them declining technical support until you install Cisco units. It's up to you whether to "risk" it, but we've seen absolutely no indication that third-party SFPs are dangerous. Just keep in mind you'll receive no help from Cisco in doing this.
Then the second command:
# no errdisable detect cause gbic-invalid
Once service unsupported-transceiver has been run, it will accept this command, which forces it to leave the port open even when an unrecognized SFP is inserted.
That's it. At this point, your Catalyst should happily accept a quality third party SFP you plug into it.
Smart Network Upgrades Save Money 
Network upgrades don't have to cost a premium. Even if you want top-quality Cisco hardware in your office, buying smaller items like SFPs from third-party vendors can significantly reduce your overall costs. The larger vendors like to lock you into their wares, and over-charge for common parts, but this can be worked around, as we see here.
If you're looking for further savings on your network, consider purchasing certified refurbished hardware. When you buy from a vendor with their own in-house shop, and guaranteed warranty, you get a purchase that's as reliable as new, at a fraction of the original costs.
You may even be able to trade in existing equipment for further savings.
For most businesses looking at network upgrades which aren't truly cutting-edge, pre-owned equipment is a cost-effective way of obtaining a great custom-built network tooled for the features you need, without unnecessary cruft.
So for a free consultation on your networking needs, or to talk about crafting a network built for your future needs, contact Hummingbird Networks with your questions!
