redundancy and load balancing between catalyst 3524-XL and catalyst3548-XL

Discussion in 'Cisco' started by jan.paulini, May 12, 2008.

  1. jan.paulini

    jan.paulini Guest

    the current situation is that we have 2 sites connected with 2
    microwave links. the links are of different brand and can not be
    redundant by them self. if one link fails i am currently shutting down
    that interface and bring up the interface for the spare link on the
    catalyst. here the current interface config:

    3548-XL
    interface FastEthernet0/43
    description ll02
    duplex full
    speed 100
    switchport trunk encapsulation dot1q
    switchport mode trunk
    .........
    interface FastEthernet0/48
    description ll01
    shutdown
    duplex full
    speed 100
    switchport trunk encapsulation dot1q
    switchport mode trunk

    and the other side the 3524-XL
    interface FastEthernet0/19
    description ll02
    duplex full
    speed 100
    switchport trunk encapsulation dot1q
    switchport mode trunk
    .........
    interface FastEthernet0/23
    description ll01
    duplex full
    speed 100
    switchport trunk encapsulation dot1q
    switchport mode trunk

    fe0/43 - fe0/19 are one link and fe0/48 - fe0/23 are one link.

    i have read about port group and have tried to configure that today, i
    can issue the commands and the config does show the ports in the port
    group but i cant pass any traffic. i had all 4 interfaces in port
    group 1. is port group the wrong thing to do for what i try to
    achieve ?

    any advice is very welcome.

    regards
    Jan
     
    jan.paulini, May 12, 2008
    #1
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  2. jan.paulini

    Trendkill Guest

    Do you have to trunk? Why not turn up a diff subnet on the remote
    side and turn up layer 3 routing between sites via both links? If one
    drops, routing will failover to the second link since the adjacency
    will drop. If you can't do this, I'm not sure why a link failure
    wouldn't failover with your configuration anyway. If you have two
    trunks, only one is being used at any given time (to avoid a loop),
    and if it fails, spanning-tree should run and it should go forwarding
    on the other trunk. What am I missing?
     
    Trendkill, May 13, 2008
    #2
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  3. jan.paulini

    Trendkill Guest

    If you want to load share, and presuming both links are equal
    bandwidth and go between the same two switches, have you tried
    etherchannel? If its just a layer 2 connection at each switch, they
    most likely have no idea that there is a microwave between them, and
    etherchannel would allow both ports to belong in the same channel
    unless one went down. Else the layer 3 suggestion from my previous
    post will work fine, as long as both links are equal bandwidth, any
    decent routing protocol should load share the paths presuming its the
    same end points on both sides.
     
    Trendkill, May 13, 2008
    #3
  4. jan.paulini

    jan.paulini Guest

    routing is not possible, for "historic" reasons i have to stick to the
    current setup. the microwave links behaving transparent to the
    switches and the switches "believe" there is a cable between them. yes
    both links have the same capabilities, 34mbit/s. i had tried just to
    enable all for interfaces and leave spanning tree do the job. i
    noticed it takes about 5 minutes for traffic to pass if the currently
    active link fails. so i was looking for something which will fail over
    within seconds. i believe port group is etherchannel on cisco
    switches, if not please elaborate, i try in the meanwhile to find some
    documentation on the web.

    thanks to both of you.

    Jan
     
    jan.paulini, May 14, 2008
    #4
  5. jan.paulini

    Bod43 Guest

    I think that the key here is 'how realistic a wire
    does the microwave link provide'.

    If it really does look like a wire to the switch and
    the port goes DOWN iif the link does then I think
    that you could use etherchannel. This uses
    port groups in its confguration statements.

    If on the other hand it is not such a good simulation
    of a wire you will I think have to use Spanning tree.
    You can do a form of load balancing with STP if you have
    more than one VLAN in use by having some VLANS use
    one link by preference and some VLANs using the other.

    By defaut STP takes 30 (35?) seconds I seem to recall
    to transition to forwarding in the event of a link failure
    in your topology. Thre is now RSTP but maybe
    your old switched do not do it.

    The timers are tunable to make convergence faster.
    Thing is you say that yours is taking 5 mins.

    Unless your timers have been changed the other way then
    something else is causing the delay.

    If you post the whole config maybe someone will have a look?
     
    Bod43, May 14, 2008
    #5
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