Are the Arista SFP transceivers compatible with Cisco switches? For example, if I go to the CDW site they show multiple transceivers that vary in price. How can I know that they will work in the Cisco 2960 switch I have?
I don't have any direct experience with arista SFP and cisco switches but the SFP interface is standardized such that it is supposed to work.
For instance, I use an Avici SFP module in a Linksys switch. I have used Juniper SFP modules in enterasys switches and Extreme branded modules in Juniper firewalls.
I have also seen weird things with copper sfp 1g modules (generic modules from CDW and Juniper branded) not working in an enterasys sfp+ interface, so it isn't 100% certain, but for something like a cisco 2960, cisco would have to have gone out of their way to break SFP compatibility, and they're big enough that I suspect they'd avoid doing that to avoid scrutiny from regulators.
Now, if it works or doesn't work, it won't be supported. It won't void your warranty or anything, but if you have weird problems related to that link, I wouldn't advertise that you're using a non-cisco branded module.
It depends of the brand and model of the SFP/Gbic
It depends of the model of the switch.
Some routers and switches will refuse to use a Non-cisco SFP (eeprom check), while some others will need the following commands to make it work (and some others just work):
switch(config)# service unsupported-transceiver switch(config)# no errdisable detect cause gbic-invalid
RP/0/RSP0/CPU0:ios#sh run int te0/0/0/0 interface TenGigE0/0/0/0 transceiver permit pid all
Some Finisar's are known to work, while some Zycko's works even without "service unsupported-transceiver".
You can also browse through Cisco-nsp mailing-list archive to find more informations about (compatible or not) vendors.
I keep running into this more and more. Swapping branded SFP's around will always cause problems, it depends if the device is checking EEPROM and what the EEPROM is holding in memory.
Rather than swap out 2 different brands of SFP I would just go for a low cost compatible. Finisar SFP's are usually a generic code to work in 'most' devices. You need to get SFP's specific to the device to be sure.
Please see this document regarding the compatibility of SFP's and also a FAQ I put together in an attempt to straighten out some of the confusion on this topic.