Cisco switches cable question

Discussion in 'Cisco' started by Mike W., Nov 13, 2007.

  1. Mike W.

    Mike W. Guest

    Hi all,

    Quick question:

    A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    that have the 1000Base-T GBIC copper adapter (Part WS-G5483).

    The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    cables to connect them?

    Thanks
    Mike W., Nov 13, 2007
    #1
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  2. Mike W.

    Trendkill Guest

    On Nov 13, 12:45 pm, "Mike W." <> wrote:
    > Hi all,
    >
    > Quick question:
    >
    > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >
    > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    > cables to connect them?
    >
    > Thanks


    It appears from the 2960 guide (link below) that MDIX is supported and
    is enabled by default. I have always elected to use crossovers just
    because it is good to have some laying around, and its a safe way to
    mitigate risks (I have had many auto-mdix issues related to IBM
    Regattas in past lives). I'm sure those issues are fixed now, be we
    had to manually disable mdix on all switchports to those servers for
    quite sometime due to nobody from either vendor (ibm, cisco) being
    able to figure out exactly what was happening on boot that would make
    the switchports change polarity.

    Anyway, I'd test first, but yes your solution should work.
    Trendkill, Nov 13, 2007
    #2
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  3. Mike W.

    Trendkill Guest

    Trendkill, Nov 13, 2007
    #3
  4. Mike W.

    Thrill5 Guest

    Gig uses all four pairs, so a standard Ethernet crossover won't work. I
    don't know if its part of the standard or not (but I think it is) gig ports
    will automatically detect when crossover is needed. Do yourself a favor and
    use a straight-thru cable and only use a crossover if that doesn't work.


    "Mike W." <> wrote in message
    news:pol_i.181450$...
    > Hi all,
    >
    > Quick question:
    >
    > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >
    > The 2960 does auto-MDIX, correct? So I can use straight-thru patch cables
    > to connect them?
    >
    > Thanks
    >
    >
    Thrill5, Nov 14, 2007
    #4
  5. On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:

    > Hi all,
    >
    > Quick question:
    >
    > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >
    > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    > cables to connect them?
    >
    > Thanks


    If you do need a crossover, this is always pretty.

    http://en.wikipedia.org/wiki/Ethernet_crossover_cable

    MikeG
    Mike Gauthier, Nov 14, 2007
    #5
  6. Mike W.

    Mike W. Guest

    Trendkill wrote:
    > On Nov 13, 12:45 pm, "Mike W." <> wrote:
    >> Hi all,
    >>
    >> Quick question:
    >>
    >> A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    >> that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >>
    >> The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    >> cables to connect them?




    Thanks for the responses to this guys....I really appreciate it.

    One other (probably dumb) question:

    I am going to have to make a couple runs with fiber to our offices that
    are on different floors of the building. The 2960 has 4 SFP fiber optic
    modules. Is there either: A cable that is SFP on one end and SC on the
    other, OR, is there an adapter that will make that conversion? I am
    trying to go from the 2960 SFP to a 3548 with a WS-G5484 module.

    Fiber is really not my thing so I'm learning as I go here....

    Thanks again,

    Mike
    Mike W., Nov 14, 2007
    #6
  7. Mike W.

    alexd Guest

    Mike W. wrote:

    > One other (probably dumb) question:
    >
    > I am going to have to make a couple runs with fiber to our offices that
    > are on different floors of the building. The 2960 has 4 SFP fiber optic
    > modules. Is there either: A cable that is SFP on one end and SC on the
    > other, OR, is there an adapter that will make that conversion? I am
    > trying to go from the 2960 SFP to a 3548 with a WS-G5484 module.


    SFP is the slot that the fibre transceiver goes into, not a type of
    connector. The type of connector you use is determined by what type of
    connector the SFP module has on it. What SFP module will you be using?

    --
    <http://ale.cx/> (AIM:troffasky) ()
    20:23:21 up 3 days, 9:01, 1 user, load average: 0.15, 0.12, 0.09
    50,000 watts of funking power
    alexd, Nov 14, 2007
    #7
  8. Mike W.

    Mike W. Guest

    alexd wrote:
    > Mike W. wrote:
    >
    >> One other (probably dumb) question:
    >>
    >> I am going to have to make a couple runs with fiber to our offices that
    >> are on different floors of the building. The 2960 has 4 SFP fiber optic
    >> modules. Is there either: A cable that is SFP on one end and SC on the
    >> other, OR, is there an adapter that will make that conversion? I am
    >> trying to go from the 2960 SFP to a 3548 with a WS-G5484 module.

    >
    > SFP is the slot that the fibre transceiver goes into, not a type of
    > connector. The type of connector you use is determined by what type of
    > connector the SFP module has on it. What SFP module will you be using?
    >



    Sorry, my bad. I'm reading up on it more now.

    What I meant to ask (I think), was a cable that is LC - SC

    I think I found one that would work:

    http://www.deepsurplus.com/10-Meter...orblackAs-low-as-46-55-font?sc=2&category=169

    ? Maybe ?

    The SFP module would be whatever can go into the 2960's mini-GBIC slots.

    Thanks
    Mike W., Nov 14, 2007
    #8
  9. Mike W.

    Trendkill Guest

    On Nov 14, 4:41 pm, "Mike W." <> wrote:
    > alexd wrote:
    > > Mike W. wrote:

    >
    > >> One other (probably dumb) question:

    >
    > >> I am going to have to make a couple runs with fiber to our offices that
    > >> are on different floors of the building. The 2960 has 4 SFP fiber optic
    > >> modules. Is there either: A cable that is SFP on one end and SC on the
    > >> other, OR, is there an adapter that will make that conversion? I am
    > >> trying to go from the 2960 SFP to a 3548 with a WS-G5484 module.

    >
    > > SFP is the slot that the fibre transceiver goes into, not a type of
    > > connector. The type of connector you use is determined by what type of
    > > connector the SFP module has on it. What SFP module will you be using?

    >
    > Sorry, my bad. I'm reading up on it more now.
    >
    > What I meant to ask (I think), was a cable that is LC - SC
    >
    > I think I found one that would work:
    >
    > http://www.deepsurplus.com/10-Meter-LC-SC-8-3-125-Singlemode-Duplex-F...
    >
    > ? Maybe ?
    >
    > The SFP module would be whatever can go into the 2960's mini-GBIC slots.
    >
    > Thanks


    Yes they make LC to SC cables as you found, and they work fine when
    connecting switches, etc. Just ensure that your other fiber stuff
    matches (micron, etc). If you can, I would avoid running new fiber
    and just jumped SC to LC on one end and always have a few spare runs
    around in case. You always should avoid running a single long cable
    that is different than the rest to avoid backing yourself into a
    corner....although sometimes you don't quite have a choice.
    Trendkill, Nov 14, 2007
    #9
  10. Mike W.

    zavrik

    Joined:
    Nov 7, 2007
    Messages:
    3
    I have a similar setup, LC - SC cables, LC end plugs into SFP module, SC into fiber patch panel/GBIC modules

    By the way,
    I can't see why not. My 6503 Catalyst and 3845 are interconnected with a standard crossover, gig ports on both ends, and works without a blink...
    zavrik, Nov 15, 2007
    #10
  11. Mike W.

    Sam Wilson Guest

    In article <>,
    Mike Gauthier <> wrote:

    > On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    >
    > > Hi all,
    > >
    > > Quick question:
    > >
    > > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    > > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    > >
    > > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    > > cables to connect them?
    > >
    > > Thanks

    >
    > If you do need a crossover, this is always pretty.
    >
    > http://en.wikipedia.org/wiki/Ethernet_crossover_cable


    But, as someone said earlier, pointless. 1000base-T uses all four pairs
    in both directions simultaneously so a straight-through cable is the
    correct thing to use. There are systems that can adapt to crossover
    cables, but it just makes things more complicated.

    Sam
    Sam Wilson, Nov 15, 2007
    #11
  12. Sam Wilson <> writes:
    >In article <>,
    > Mike Gauthier <> wrote:
    >> On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    >> > Quick question:
    >> >
    >> > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    >> > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >> >
    >> > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    >> > cables to connect them?


    >> If you do need a crossover, this is always pretty.
    >>
    >> http://en.wikipedia.org/wiki/Ethernet_crossover_cable


    >But, as someone said earlier, pointless. 1000base-T uses all four pairs
    >in both directions simultaneously so a straight-through cable is the
    >correct thing to use. There are systems that can adapt to crossover
    >cables, but it just makes things more complicated.



    Not so pointless, especially with Cisco gear.

    Doing a Gigabit between Cisco GBIC switchport to Cisco GBIC switchport
    *requires* a true (ie. all 4 pair) ethernet cross-over cable. Cisco
    did not support auto MDI/MDI-X on their old-gear GBIC copper switchports.
    You generally had to make them yourself, since vendors are so lazy and
    made only half-correct cables in general.

    Thankfully, they do on modern gear, and it shouldn't matter to the OP,
    since he's using one modern to one old-school.
    Doug McIntyre, Nov 15, 2007
    #12
  13. Mike W.

    Thrill5 Guest

    "Doug McIntyre" <> wrote in message
    news:473c8d5c$0$90430$...
    > Sam Wilson <> writes:
    >>In article <>,
    >> Mike Gauthier <> wrote:
    >>> On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    >>> > Quick question:
    >>> >
    >>> > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few
    >>> > 3548's
    >>> > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >>> >
    >>> > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    >>> > cables to connect them?

    >
    >>> If you do need a crossover, this is always pretty.
    >>>
    >>> http://en.wikipedia.org/wiki/Ethernet_crossover_cable

    >
    >>But, as someone said earlier, pointless. 1000base-T uses all four pairs
    >>in both directions simultaneously so a straight-through cable is the
    >>correct thing to use. There are systems that can adapt to crossover
    >>cables, but it just makes things more complicated.

    >
    >
    > Not so pointless, especially with Cisco gear.
    >
    > Doing a Gigabit between Cisco GBIC switchport to Cisco GBIC switchport
    > *requires* a true (ie. all 4 pair) ethernet cross-over cable. Cisco
    > did not support auto MDI/MDI-X on their old-gear GBIC copper switchports.
    > You generally had to make them yourself, since vendors are so lazy and
    > made only half-correct cables in general.
    >
    > Thankfully, they do on modern gear, and it shouldn't matter to the OP,
    > since he's using one modern to one old-school.
    >

    1000Base-T GBICs absolutely support auto MDIX. I have about 60 3550's in
    closets that are connected together via GBIC's and connected to 6500's all
    using straight-through cables
    Thrill5, Nov 15, 2007
    #13
  14. Mike W.

    Gary Guest

    Mike W. wrote:
    > Is there either: A cable that is SFP on one end and SC on the
    > other, OR, is there an adapter that will make that conversion?


    Belkin makes a whole litter of fiber cables with different kinds of
    connectors. But I think CablesToGo have patch cables that may be more
    handy if you've already got a run in place. If you're replacing your
    current cable run and depending on the length, you may just want to have a
    new one made by a professional -- unlike ethernet cables, I wouldn't
    recommend investing in the hardware and testing equipment to make them
    yourself unless you plan on doing this on a regular basis.

    -Gary
    Gary, Nov 15, 2007
    #14
  15. "Thrill5" <> writes:
    >"Doug McIntyre" <> wrote in message
    >> Not so pointless, especially with Cisco gear.
    >>
    >> Doing a Gigabit between Cisco GBIC switchport to Cisco GBIC switchport
    >> *requires* a true (ie. all 4 pair) ethernet cross-over cable. Cisco
    >> did not support auto MDI/MDI-X on their old-gear GBIC copper switchports.
    >> You generally had to make them yourself, since vendors are so lazy and
    >> made only half-correct cables in general.


    >1000Base-T GBICs absolutely support auto MDIX. I have about 60 3550's in
    >closets that are connected together via GBIC's and connected to 6500's all
    >using straight-through cables


    Okay, should have quantified, some gear taking GBIC copper will do it.
    I wasn't trying to imply it was the GBIC limitation, but rather the
    age of the gear. Some of the old Cisco gear with GBIC slots do not
    do auto MDI/MDI-X on the GBIC slots.
    Doug McIntyre, Nov 15, 2007
    #15
  16. On Thu, 15 Nov 2007 12:06:01 +0000, Sam Wilson wrote:

    > In article <>,
    > Mike Gauthier <> wrote:
    >
    >> On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    >>
    >> > Hi all,
    >> >
    >> > Quick question:
    >> >
    >> > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few
    >> > 3548's that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    >> >
    >> > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    >> > cables to connect them?
    >> >
    >> > Thanks

    >>
    >> If you do need a crossover, this is always pretty.
    >>
    >> http://en.wikipedia.org/wiki/Ethernet_crossover_cable

    >
    > But, as someone said earlier, pointless. 1000base-T uses all four pairs
    > in both directions simultaneously so a straight-through cable is the
    > correct thing to use. There are systems that can adapt to crossover
    > cables, but it just makes things more complicated.
    >
    > Sam


    *IF* he needs or wants one, the referenced URL has the information (both
    10/100base-T and 1000base-T) he is looking for. Or did you not actually
    read what I wrote?

    MikeG
    Mike Gauthier, Nov 16, 2007
    #16
  17. Mike W.

    Sam Wilson Guest

    In article <473c8d5c$0$90430$>,
    Doug McIntyre <> wrote:

    > Sam Wilson <> writes:
    > >In article <>,
    > > Mike Gauthier <> wrote:
    > >> On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    > >> > Quick question:
    > >> >
    > >> > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few 3548's
    > >> > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    > >> >
    > >> > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    > >> > cables to connect them?

    >
    > >> If you do need a crossover, this is always pretty.
    > >>
    > >> http://en.wikipedia.org/wiki/Ethernet_crossover_cable

    >
    > >But, as someone said earlier, pointless. 1000base-T uses all four pairs
    > >in both directions simultaneously so a straight-through cable is the
    > >correct thing to use. There are systems that can adapt to crossover
    > >cables, but it just makes things more complicated.

    >
    >
    > Not so pointless, especially with Cisco gear.
    >
    > Doing a Gigabit between Cisco GBIC switchport to Cisco GBIC switchport
    > *requires* a true (ie. all 4 pair) ethernet cross-over cable. Cisco
    > did not support auto MDI/MDI-X on their old-gear GBIC copper switchports.
    > You generally had to make them yourself, since vendors are so lazy and
    > made only half-correct cables in general.


    I don't doubt your experience, but WHY? Have a look at the 1000base-T
    description (figure 7.23 at
    <http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ethernet.htm>
    for instance) and wonder why on earth anyone would ever think of using a
    crossover. Any kind of auto-MDI behaviour should only be to correct the
    erroneous use of a crossover cable!

    > Thankfully, they do on modern gear, and it shouldn't matter to the OP,
    > since he's using one modern to one old-school.


    Shouldn't matter.

    Sam
    Sam Wilson, Nov 16, 2007
    #17
  18. Mike W.

    Sam Wilson Guest

    In article <>,
    "Thrill5" <> wrote:

    > "Doug McIntyre" <> wrote in message
    > news:473c8d5c$0$90430$...
    > > Sam Wilson <> writes:
    > >>In article <>,
    > >> Mike Gauthier <> wrote:
    > >>> On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    > >>> > Quick question:
    > >>> >
    > >>> > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few
    > >>> > 3548's
    > >>> > that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    > >>> >
    > >>> > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    > >>> > cables to connect them?

    > >
    > >>> If you do need a crossover, this is always pretty.
    > >>>
    > >>> http://en.wikipedia.org/wiki/Ethernet_crossover_cable

    > >
    > >>But, as someone said earlier, pointless. 1000base-T uses all four pairs
    > >>in both directions simultaneously so a straight-through cable is the
    > >>correct thing to use. There are systems that can adapt to crossover
    > >>cables, but it just makes things more complicated.

    > >
    > >
    > > Not so pointless, especially with Cisco gear.
    > >
    > > Doing a Gigabit between Cisco GBIC switchport to Cisco GBIC switchport
    > > *requires* a true (ie. all 4 pair) ethernet cross-over cable. Cisco
    > > did not support auto MDI/MDI-X on their old-gear GBIC copper switchports.
    > > You generally had to make them yourself, since vendors are so lazy and
    > > made only half-correct cables in general.
    > >
    > > Thankfully, they do on modern gear, and it shouldn't matter to the OP,
    > > since he's using one modern to one old-school.
    > >

    > 1000Base-T GBICs absolutely support auto MDIX. I have about 60 3550's in
    > closets that are connected together via GBIC's and connected to 6500's all
    > using straight-through cables


    Yeah - we have a variety of 3Coms and Cisco switches with 10/100/1000
    interfaces and GBICs/SFPs. I've never knowingly used a crossover cable
    to connect them together.

    Sam
    Sam Wilson, Nov 16, 2007
    #18
  19. Mike W.

    Sam Wilson Guest

    In article <473cc764$0$90424$>,
    Doug McIntyre <> wrote:

    > "Thrill5" <> writes:
    > >"Doug McIntyre" <> wrote in message
    > >> Not so pointless, especially with Cisco gear.
    > >>
    > >> Doing a Gigabit between Cisco GBIC switchport to Cisco GBIC switchport
    > >> *requires* a true (ie. all 4 pair) ethernet cross-over cable. Cisco
    > >> did not support auto MDI/MDI-X on their old-gear GBIC copper switchports.
    > >> You generally had to make them yourself, since vendors are so lazy and
    > >> made only half-correct cables in general.

    >
    > >1000Base-T GBICs absolutely support auto MDIX. I have about 60 3550's in
    > >closets that are connected together via GBIC's and connected to 6500's all
    > >using straight-through cables

    >
    > Okay, should have quantified, some gear taking GBIC copper will do it.
    > I wasn't trying to imply it was the GBIC limitation, but rather the
    > age of the gear. Some of the old Cisco gear with GBIC slots do not
    > do auto MDI/MDI-X on the GBIC slots.


    At the risk of repeating myself, what on earth does the MDI/MDI-X
    distinction mean in the context of a connection that is inherently
    straight-through in both directions?

    Sam
    Sam Wilson, Nov 16, 2007
    #19
  20. Mike W.

    Sam Wilson Guest

    In article <>,
    Mike Gauthier <> wrote:

    > On Thu, 15 Nov 2007 12:06:01 +0000, Sam Wilson wrote:
    >
    > > In article <>,
    > > Mike Gauthier <> wrote:
    > >
    > >> On Tue, 13 Nov 2007 17:45:20 +0000, Mike W. wrote:
    > >>
    > >> > Hi all,
    > >> >
    > >> > Quick question:
    > >> >
    > >> > A 2960 (WS-C2960G-48TC-L) with 40 copper Gb ports, going to a few
    > >> > 3548's that have the 1000Base-T GBIC copper adapter (Part WS-G5483).
    > >> >
    > >> > The 2960 does auto-MDIX, correct? So I can use straight-thru patch
    > >> > cables to connect them?
    > >> >
    > >> > Thanks
    > >>
    > >> If you do need a crossover, this is always pretty.
    > >>
    > >> http://en.wikipedia.org/wiki/Ethernet_crossover_cable

    > >
    > > But, as someone said earlier, pointless. 1000base-T uses all four pairs
    > > in both directions simultaneously so a straight-through cable is the
    > > correct thing to use. There are systems that can adapt to crossover
    > > cables, but it just makes things more complicated.
    > >
    > > Sam

    >
    > *IF* he needs or wants one, the referenced URL has the information (both
    > 10/100base-T and 1000base-T) he is looking for. Or did you not actually
    > read what I wrote?


    I read exactly what you wrote. I'm just finding it hard to conceive any
    circumstance (and of course I bow to experience) where 1000base-T would
    require a crossover cable.

    Sam
    Sam Wilson, Nov 16, 2007
    #20
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