2950 load balancing cluster with etherchannel uplink to core-switch

Discussion in 'Cisco' started by Thoralf Will, Feb 21, 2005.

  1. Thoralf Will

    Thoralf Will Guest


    I couldn't find anything matching my question (yet), so I hope to get
    an answer here.

    1 rack with 2 Cisco 2950 has to be connected redundant via 2x 100MBit
    uplinks to the datacenter-switches. Each server in this rack has 2
    network connections to each of the switches. Each switch has its own
    uplink and both switches should have an interconnection to handle
    internal traffic that might come in on 1 switch and has to be
    transfered via the other switch to the target. Each server has a
    primary interface that it is usually using and is able to
    transparently switch over to the other interface if a link down is
    recognized (bonding). So it might be possible that server1 is using
    switch1 while server2 is using switch2 for some reason. This traffic
    has to be kept inside the rack, therefor the interconnection is

    How to configure the 2 switches to provide as much redundancy and
    reliability as possible?

    I build a cluster of these 2950 to get internal redundancy. 2x100MBit
    interconnection (I do not have GBICs) should be enough to handle the
    traffic easily and provide enough reliability in case 1 connection
    breaks down. Each switch gets one physical uplink configured as
    etherchannel loadbalancing.

    Is this possible and how? I'm not a cisco-expert but willing and able
    to learn quite fast, so suggestions and hints are very much welcome.

    Thanks in advance,

    PS: Just in case the question comes up: "Why don't you ask your data
    center to do this for you?" - I did (well, the management did) but
    they aren't able to do this as it seems so it's up to me to find a
    solution now.
    Thoralf Will, Feb 21, 2005
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  2. Thoralf Will

    Colin Cant Guest


    build up an cisco etherchannel bedween the two 2950 in the rack using 2 up
    to 8 x 100Mbit lines and trunk em together as one physical link. that should
    do for speed and stability bedween these two, since you havent got some
    gbics. now for the servers u could configure them with i think, uuhm, its
    called M$ NLB. Using 1 ip address via 2 network cards.
    now u connect as you suggested one server to each switch
    and the hole bundle u connect as following to ure backbone:

    variant 1
    connect the first switch again via etherchannel to youre router.
    the same for the second switch. here u need to work with spanning tree
    u always got 2 wires connecting each device like this. speed and stability

    variant 2
    connect switch 1+2 each witch etherchannels to youre first internal router
    connect switch 1+2 each witch etherchannels to youre backup internal router
    (or rootswitch for vlan definitions if in vtp server mode)
    then connect these 2 internal routers to youre providers router. now the
    single point of failure is the router of youre provider and just the single
    line out of youre house into www. but i'm sure youre ISP could handle that.

    i'm aswell not a cisco professional, currently workin in ms client support
    but getting closer to the world of cisco hehe ;-)
    but it perhaps got some info for u could use.

    PS: etcherchannels need same link speed and even same throughput over the
    wires! execpt someone could tell me this is false. :))
    greetings Colin
    Colin Cant, Feb 24, 2005
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  3. Thoralf Will

    thrill5 Guest

    Since you have server connected to two different switches, it is very
    important that the server NICs are configured for fault-tolerance NOT
    load-balancing. If they are configured for load-balancing your 2950's will
    get very confused because the MAC address of the server will continuously
    bounce between the connected port on the local port and the up-link port to
    the other switch.

    thrill5, Feb 27, 2005
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