Question on an SFP connector.

Shoe BoxShoe Box Banned Posts: 118
I have seen the SFP connectors which can attach a pair of fiber optic lines, and plug into an Ethernet port.

But my question is, are they made for regular or fast ethernet ports, or do they HAVE to go into a gigabit ethernet port?

This: Cisco MFEFX1 100 Base-FX Mini-GBIC SFP Transceiver - MFEFX1 - Ethernet Transceivers -


  • thomas_thomas_ CompTIA N+/S+/L+ CCNA R&S CCNP R&S/Enterprise/Collab Member Posts: 991 ■■■■■■■□□□
    You don't plug them into ethernet ports, you plug them into "expansion slots" on the switch or router. From my understanding the SFPs aren't able to negotiate speed so you had an older switch that could only do 100Mbps on one side and a newer switch with the 1Gbps SFP connector it wouldn't work because you can't change the speed of the SFP.

    If you have 100Mbps SFP on one side and a newer switch that did 1Gbps on the other it would work because the newer Gigabit ethernet switch would be able to sense the speed or you could manually change the speed of that port.
  • Shoe BoxShoe Box Banned Posts: 118
    According to this, which I just found, they can go into a Gigabit Ethernet port. I just could not find any photos of the back side of the connector, and I see no locking tab like that plastic tab on a normal Ethernet cable.

    Cisco SFP Modules for Gigabit Ethernet Applications Data Sheet - Cisco
  • thomas_thomas_ CompTIA N+/S+/L+ CCNA R&S CCNP R&S/Enterprise/Collab Member Posts: 991 ■■■■■■■□□□
    The link you provided does say "Gigabit ethernet port or slot", but I think that is really just referring to the SFP slot which is rectangular. You can see a picture of an SFP slot in the following picture on the left hand side below the DB-9 console connection there are two of them side by side:

    To my knowledge there is no SFP connector that you can plug into a regular port on a switch that normally has a cable with a RJ-45/8P8C connector plugged into it..
  • thomas_thomas_ CompTIA N+/S+/L+ CCNA R&S CCNP R&S/Enterprise/Collab Member Posts: 991 ■■■■■■■□□□
  • slinuxuzerslinuxuzer Member Posts: 665 ■■■■□□□□□□
    your question is highly relative, you would have to determine this on a case by case basis. You would need to check compatibility for that specific optic against the specific switch. with that said, I personally have never worked with a switch where the dedicated uplink ports are 10 megabit, that would have to be a really really old device. Typically you have your 12/24/48 ports at a lower speed and then 2-4 ports off to the right at the next speed increment that use an expansion slot to provide maximum flexibility to connect to upstream switches.

    I have worked with many switches where the expansion ports were 1/10/40 gigabit Ethernet.
  • EdificerEdificer Member Posts: 185
    We are using GT-802S SX/LX Gigabit Media converters, this is something that might interest you

    Specific criteria that need to match before purchasing these
    fiber type: SW or LW
    speed: 100Base or 1000Base

    100Base media converter for a 1000Base switch will not work. So, only purchase a 100Base if you are using Fa switches
    “Our greatest glory is not in never falling, but in rising every time we fall.” ― Confucius
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