Cisco: Are SR and LR modules compatible at all?

stateless · 05-21-2014, 07:30 PM

Kind of new to this... but doing some entry level networking work involving 10Ge fiber and cisco switches/hosts. Someone was asking about this: Both endpoints will need to be either SR/SR or LR/LR, right? I mean, an SR module can't "drop down" to LR, or the other way around, right? That was my impression, but I'm having trouble finding an authoritative statement to that effect.

Also, the SR and LR modes need different cable types right? (This was my impression.) Or is there a cable type that works for both?

smallpond · 05-22-2014, 12:20 PM

As a rule of thumb, you should make a connection between identical transceiver part numbers. You at least need to match the frequency and the cable type. Cable in general is single-mode fibre for LR and multimode for SR. Frequency is 850, 1300 or 1550 nm. Don't mix and match. The one characteristic that doesn't seem to matter much is core size of multimode cable. I've never seen using different sizes cause a problem. See here:

http://www.cisco.com/c/en/us/td/docs.../78_15160.html