Correct way to connect a 2900 with a 2950

Discussion in 'Cisco' started by stonent, May 3, 2005.

  1. stonent

    stonent Guest

    I'm adding a 2950 to a rack with mostly 2900 and 1900's. I need to
    connect the 2950 to the hub above it and was told by our datacom guy
    that I needed to connect Bx on the hub above to Ax on the 2950. I did
    but got no lights. So then I tried a crossover cable and got an orange
    light. The computers on the 1 through 24 ports could not get an IP. So
    I connected port 5 to port 5 using a crossover cable and was able to
    get it "working" I know this isn't the correct way to do this but
    wanted to check in and see if there were any other suggestions.

    The datacom guy said an orange light means that there was a problem
    with the connection between Bx and Ax.

    There are no special settings on this equipment and as far as I know
    they are all running with an out of the box configuration.
    stonent, May 3, 2005
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  2. stonent

    Nick Guest

    first off, you need to use a crossover cable (hence the orange light you
    got), so your good there.

    second, check the speed of the hub. If its 10mb, you will have a
    problem using an uplink port. I haven't used a 2950 with an Ax and Bx
    port, only 1900's, but I do know they are locked at 100mb and I assume
    the 2950 is the same.

    As a suggestion, I would plug the 2950 into another switch in the rack
    (1900 or another 2900) on a 100mb port so you can keep the backbone
    100mb. Take the hub and hang it off one of the "numbered" ports on the
    last switch. This way all of the traffic on the 2950 won't be fighting
    a 10mb link and contending with the traffic on the hub.
    Nick, May 4, 2005
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  3. stonent

    Peter Guest

    Here are a couple of ideas...
    Yes, a X-over is needed, however please note that the 1900 A/B ports
    are fixed at 100Mb and default to Full Duplex. They don't do 10Mb (or
    Gig). The A/B ports on the 2950 can do 10/100/1GB and Half/Full
    (except Gig which is only Full), so you may need to lock those ports
    to match the 1900. I can't remember if the 1900 does Autonegotiate on
    these ports, probably not, so locking all ports is probably best....
    If Autonegotiate fails it defaults to 10Mb Half Duplex, which is why
    the light stays orange, the 1900 only does 100Mb...

    I also take your reference to "HUB" above to mean Switch and not a
    true HUB. If its a true hub then remember that a Hub is always Half
    Duplex, unless it is a "Switched Hub" when all bets are
    The 1900 non A/B ports are fixed at 10/Half, which is the default for
    the 2950 autonegotiate that does not get a negotiate response, so you
    probably got lucky with that connection.........;-)
    Yes, it means the Autonegotiate on the 2950 failed to complete and
    there is a link mismatch with the result. Locking both ends to the
    same setting (100/Full) should allow it to work fine...
    On a 2950 gig port use -
    duplex full
    speed 100
    to remove autonegotiate.

    Peter, May 5, 2005
  4. stonent

    stonent Guest

    Yeah, switch not hub. I know the difference, but the datacom guy calls
    everything a hub so I got used to using that term around him.

    I've since returned to the closet and found some other things.
    Actually all of our 2900's are 24 port and have no Ax/Bx ports. The
    1900's are 24 port and have 100Mbit Ax/Bx ports. So the connections
    from the 1900's to 2900's are done from Bx on the 1900 to a numbered
    port on the 2900. I suspect I should reverse this on the 2950. I
    should probably go from a numbered port on the 2900 to the Ax port on
    the 2950. (Initially I was going Bx on the 1900 to Ax on the 2950,
    which may have been the problem since no one has changed any of the
    factory settings on the new switch.)

    Of course the question is why have they not been configured? Well we
    don't have any people in this office that do that sort of thing. I
    might try my hand at it. I'll just load up Ethereal and leave a sniff
    running for a while and filter out everything but the cisco to cisco
    traffic and hopefully I'll see the MAC of the switch and then can
    figure out what IP it grabbed off of dhcp.
    stonent, May 9, 2005
  5. stonent

    Peter Guest

    Sounds typical, I just like to make sure didn't miss
    That shouldn't be a problem, the 2900's can do 100/Full on those ports
    so that can match the 1900's A/B ports.
    I don't see why that is necessary, the A/B ports both operate exactly
    the same, and are compatible with any of the 24 ports on the 2900. Its
    just a case of ensuring the Speeds and Duplex's match for each
    connection to a 1900...
    For the 2900's, think of Gig ports (equivalent to A/B) as identical to
    the 24 standard ports, except they can do 1GB as well. On the 2900's
    ALL ports can do trunking etc, but on the 1900's only the A/B pors can
    do that.
    Peter, May 11, 2005
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