multilayer router trunking?

Discussion in 'Cisco' started by lfnetworking, Jun 16, 2005.

  1. lfnetworking

    lfnetworking Guest

    I have 2 dot1q trunk fe interfaces on a 7206 connected to two different
    35xx switches. Currently each L3 vlan subint is defined on one or the
    other router trunk port and switch. Given the fact that, I can't have
    two vlan subints on the same network on the same router, if I trunk the
    two 35xx's is there a way to create an alternate path via the other
    switch/router trunk int?

    thanks
     
    lfnetworking, Jun 16, 2005
    #1
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  2. lfnetworking

    Ivan Ostres Guest

    In article <ginse.3298$>,
    _bill_@_lfnetworking.com says...
    > I have 2 dot1q trunk fe interfaces on a 7206 connected to two different
    > 35xx switches. Currently each L3 vlan subint is defined on one or the
    > other router trunk port and switch. Given the fact that, I can't have
    > two vlan subints on the same network on the same router, if I trunk the
    > two 35xx's is there a way to create an alternate path via the other
    > switch/router trunk int?
    >


    If you want to have the same network (VLAN) on both switches, why not
    just trunk switches together and than trunk just one to 7206?

    One other thing is usage of IRB so you can bridge your vlan
    subinterfaces and put address only on IRB interface (per vlan) so your
    switches would comunicate on L2 on the same VLAN and using L3 between
    VLANs. This could be bad because L2 traffic would be bridged over your
    router. I would better do the first combination.


    --
    Ivan

    *** User rot13 to see my eMail address ***
     
    Ivan Ostres, Jun 17, 2005
    #2
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  3. lfnetworking

    lfnetworking Guest

    Ivan Ostres wrote:
    > In article <ginse.3298$>,
    > _bill_@_lfnetworking.com says...
    >
    >>I have 2 dot1q trunk fe interfaces on a 7206 connected to two different
    >>35xx switches. Currently each L3 vlan subint is defined on one or the
    >>other router trunk port and switch. Given the fact that, I can't have
    >>two vlan subints on the same network on the same router, if I trunk the
    >>two 35xx's is there a way to create an alternate path via the other
    >>switch/router trunk int?
    >>

    >
    >
    > If you want to have the same network (VLAN) on both switches, why not
    > just trunk switches together and than trunk just one to 7206?
    >
    > One other thing is usage of IRB so you can bridge your vlan
    > subinterfaces and put address only on IRB interface (per vlan) so your
    > switches would comunicate on L2 on the same VLAN and using L3 between
    > VLANs. This could be bad because L2 traffic would be bridged over your
    > router. I would better do the first combination.
    >
    >

    my apologies for being unclear. there are two 7206s each trunked to
    each of the two 35xxs. i'm trying to figure out how to get maximum
    redundancy.
     
    lfnetworking, Jun 20, 2005
    #3
  4. lfnetworking

    Ivan Ostres Guest

    In article <K9ote.30907$>,
    _bill_@_lfnetworking.com says...
    > my apologies for being unclear. there are two 7206s each trunked to
    > each of the two 35xxs. i'm trying to figure out how to get maximum
    > redundancy.
    >


    This is more like a philosophical question. Well, you could do it in
    many ways:

    1) you could do everything on L3 so you could trunk every 7206 to every
    switch and use HSRP or similar protocol

    2) you could connect 7206 together and switches together and still do
    IRB on routers so you would get L2 redundancy. The only thing important
    here is to figure out what happens when one of your L2 links is down, if
    the routing is still correct.

    As always, I would pick first option since I have some really bad
    (actually BAD) experiences with IRB (not on 7206 but....).


    --
    Ivan

    *** User rot13 to see my eMail address ***
     
    Ivan Ostres, Jun 20, 2005
    #4
  5. lfnetworking

    lfnetworking Guest

    Ivan Ostres wrote:
    > In article <K9ote.30907$>,
    > _bill_@_lfnetworking.com says...
    >
    >>my apologies for being unclear. there are two 7206s each trunked to
    >>each of the two 35xxs. i'm trying to figure out how to get maximum
    >>redundancy.
    >>

    >
    >
    > This is more like a philosophical question. Well, you could do it in
    > many ways:
    >
    > 1) you could do everything on L3 so you could trunk every 7206 to every
    > switch and use HSRP or similar protocol
    >
    > 2) you could connect 7206 together and switches together and still do
    > IRB on routers so you would get L2 redundancy. The only thing important
    > here is to figure out what happens when one of your L2 links is down, if
    > the routing is still correct.
    >
    > As always, I would pick first option since I have some really bad
    > (actually BAD) experiences with IRB (not on 7206 but....).
    >
    >

    thanks for responding ivan. yes, option 1 is the approach i'm referring
    to, but, my specific question at this point is if all traffic destined
    for a given routable dot1q subinterface on the routers can get to it via
    either of the trunks to the two switches. in other words the sub int
    for a given vlan can only be defined on one router trunk interface, but,
    i'm also thinking trunks carry all vlan traffic (or can be confdigured
    to do so, at any rate), so can the dot1q trunk on the same router pass
    the traffic to the router and in a way that it will get routed
    correctly? kind of convoluted question - i hope it's clear.
     
    lfnetworking, Jun 20, 2005
    #5
  6. lfnetworking

    Ivan Ostres Guest

    In article <zoEte.425$>,
    _bill_@_lfnetworking.com says...
    > thanks for responding ivan. yes, option 1 is the approach i'm referring
    > to, but, my specific question at this point is if all traffic destined
    > for a given routable dot1q subinterface on the routers can get to it via
    > either of the trunks to the two switches.
    > in other words the sub int
    > for a given vlan can only be defined on one router trunk interface, but,
    > i'm also thinking trunks carry all vlan traffic (or can be confdigured
    > to do so, at any rate), so can the dot1q trunk on the same router pass
    > the traffic to the router and in a way that it will get routed
    > correctly? kind of convoluted question - i hope it's clear.
    >


    Now I have to ask the question: do you have the same VLAN's (networks)
    on both switches? Are the switches somehow connected directly?

    --
    Ivan

    *** User rot13 to see my eMail address ***
     
    Ivan Ostres, Jun 21, 2005
    #6
  7. lfnetworking

    Guest

    The reason that you are having a hard time figuring
    out a solution to this is that you are asking the wrong
    question, one which may have no answer, (well no elegant
    answer anyway and what other kind do we want?).

    Two routers, two switches, connect each router to each
    switch with a trunk, connect the two switches with redundant trunks,
    HSRP done.
    Redundant link needed to AVOID split network in the event
    of trunk link failure.

    My guess is that
    adding unnecessarily to this design will
    not produce a more reliable network.

    "i'm trying to figure out how to get maximum
    redundancy."

    Just go for ordinary redundancy instead.

    Sorry if this is a bit terse but, however
    I do not have time to try to fix it right now.
     
    , Jun 22, 2005
    #7
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