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New Member

Cat6 or fiber

We currently run fiber with our 1900's and 2924xl's. We are looking to upgrade to the 3750G and can't find if it will be compatible with our current fiber setup. Do SFP ports work with the type of fiber ports on the 1900 and 2924's?


Re: Cat6 or fiber

Your 1900 and 2924XL switches with built-in fiber ports are running 100BaseFX (Fast Ethernet) over multimode fiber. Fast Ethernet over multimode is good to 2,000 meters max. if the connection is running in full duplex mode (only 412 meters max. if running in half duplex).

The SFPs that go into 3750G switches are for 1000Base-X (Gigabit Ethernet). They are not meant to be connected to 100BaseFX ports, and will not work if you try it. Gigabit SFPs can use multimode fiber to talk to other Gigabit fiber ports, though. Distance is limited to 220 to 275 meters when using the SX wavelength SFPs; 550 meters standard (or 700 meters max.) when using LX/LH SFPs and mode conditioning patch cables. Cisco Gigabit fiber ports run in full duplex mode only.

If you want to connect your 1900's and 2924XL's to the 3750G using multimode fiber, you will need Fast Ethernet media converters to do this at the 3750G end. Each one takes the 100BaseFX multimode feed they receive from the remote switch and converts it to a 100BaseTX signal that you can patch into any of the 10/100 or 10/100/1000 copper ports on the 3750G.

There are several manufacturers out there that make these media converters; I have found the ones from Transition Networks ( work well.

Hope this helps.

New Member

Re: Cat6 or fiber

So if I have all gigabit switches with these sfp ports, can I use my existing fiber and just put new ends on them or what?


Re: Cat6 or fiber

Yes, that is correct. Within the distance restrictions, of course.

You will need new patch cables for the connections to the SFP ports, they use the LC connector type (vs. the SC connectors found on your 100BaseFX or Gigabit GBIC interfaces).

And if you use LX/LH SFPs with multimode, you may have to look around a bit for mode conditioning patch cables with LC connectors: I'm sure somebody's making them, but I personally haven't seen them yet.