We tried to connect two buildings using fiber cable. One building has Catalyst 3520 and other building has 3750. But they don't talk to each other.
To find out the problem, we bring these two switches in the same room and connect them directly with a 5 feet fiber cable. They still have the same problem. The following are what i try so far.
1. Connecting between two 3500 switches directly.
2. Connecting between 3750 and 3500 switches directly.
3. I also tried different fiber cable.
4. The sh int shows ?GigabitEthernet0/1 is down, line protocol is down?. What could be the problem?
By the way, the blues are long range. It is not recommended to use them on anything less than 10s of meters. Normall I swap them with SX when moving them side by side. Also, I have some 62.5 micron multimode that won't work without the mode conditioning patch cables (about $200 EA). Most of my fiber works OK with multimode but the LX on long multimode can be a big problem if you are unlucky enough to get some fiber susceptible to the problem.
I assume you already know this, but just in case:
1. Make sure you are connecting SX to SX transcievers. SX and LX use different wavelengths.
2. On "show interface" make sure the ports are not in an err-disabled state and that the media type says SX (or LX) instead of unknown or unsupported, etc.
3. Be careful to make sure all you fiber is the same. We recently had someone try to patch 62.5 on to 50 micron, and it would not work.