how to get layer 2 trough layer 3 ?

Discussion in 'Cisco' started by C Cant, Apr 15, 2005.

  1. C Cant

    C Cant Guest

    hi ng,

    how do i get layer 2 comunication trough layer 3?
    i need to get cisco vlan information over a router. how do i do that? hints
    tips suggestions, anything is welcome.
    thank you colin
    C Cant, Apr 15, 2005
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  2. C Cant

    Ivan Ostres Guest

    You could use tunneling with GRE and bridging (not very smart solution)
    or you could use one of the available methods like L2TP or AoMPLS,
    depends on your use and if it it just one rotuer or a number of them.
    Ivan Ostres, Apr 15, 2005
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  3. C Cant

    C Cant Guest

    hi Ivan,

    thank you for your help, its still all about my problem mentioned in the
    "Fallback bedween a Laserlink and a HDSL modem line" post.

    ok, could you give me some hints where to start wenn i dlike to push dot1q
    traffic with your suggestions through this here

    i think i have put a router there where my switches currently are, connect
    it to the laser /modem and then connect each router to my building switch.
    i'm still not getting this right.
    C Cant, Apr 15, 2005
  4. C Cant

    C Cant Guest

    how about taking two cat 3550 and use 802.1q tunneling on these tho
    3550-SMIs in the middle witch are directly attached to the laser and the
    modem. As decribed here
    Updated version:
    put the dot1q trunkport on the"edge" switches. then i just need a to give
    the two 3550er in the middle for each line a own vlan and a management ip.
    now via this management ips i could base my routing of that tunneling port.
    and like this i could make sure the traffic gets over the interface witch
    passes the traffic through. what kind of routing protocol could i use on a
    3550er? if this should workout.
    C Cant, Apr 15, 2005
  5. C Cant

    Scooby Guest

    May I ask why you want to do that? Perhaps there is a better solution to
    what you are trying to do.
    Scooby, Apr 15, 2005
  6. C Cant

    C Cant Guest

    we got a vtp server in building A, and some departements in building B.
    both buildings need the same vlan definitions. the buildings are connected
    like the picture i put the link in the previous posts. now with fogy weather
    we got some real problems. And for that reason we need a automatic failover
    system. Spanntree does not workout for this, and so does etherchannel.
    now, thats what im looking for ;-)

    C Cant, Apr 15, 2005
  7. C Cant

    Scooby Guest

    Unless there is something very siginificant about your network setup that is
    not reflected in the graphics, I still don't understand why you need the
    same vlans in both locations. Each 3550 can be a vtp server for the
    location it is at. Don't use vlans between them, use L3 and a routing
    protocol. The routing protocol can be your failover. The end devices will
    be on separate subnets. Or, is there a reason that both ends will need to
    share a vlan/subnet? I'm not a fan of broadcasting over WAN links.

    Scooby, Apr 15, 2005
  8. C Cant

    Ivan Ostres Guest

    How often does your vlans change? How often do you delete or add vlans?
    It is a common thing to disable vtp because it can do much more trouble
    in networks than it makes administration easier.

    I would still use L3 for laser and backup links and do the following:

    If you need to have the same broadcast domains and still have routers in
    between, why not try to use GRE tunnel for every VLAN and do a bridging
    between VLAN and GRE? I've never tried it, but it might work (if I get
    some time, I will try it)....
    Ivan Ostres, Apr 15, 2005
  9. C Cant

    C Cant Guest

    still don't understand why you need the same vlans in both locations
    we want to keep administration as little as possible. we get our vlan
    definitions from the main building, vlans change pretty fast at our place,
    so there is a lot of changes, and nobody likes to do the hole configs twice
    or three times... there are several buildings attached the same way via
    its about 250 up to 500 meters laser line ;-)

    @ Ivanwhat do i need for this suggestion?

    another question about spanntree, what happens if you build up two 3550er
    connect each from fa0/1 to fa0/1 and fa0/2 to fa0/2. now each fa0/1 is in
    vlan 10 and fa0/2 is in vlan20.
    as vlan ip one would have a the other .3
    or of course for vlan 20 192.168.20.X
    would spanntree block one side or would both sides be up? physical its a
    loop, but since there are 2 diffrent vlans?
    since i then would have a layer 3 ip on the other side would this then not
    be posible to route it?
    C Cant, Apr 18, 2005
  10. C Cant

    Ivan Ostres Guest

    That should work ok.
    There would be two different spanning trees (if using PVST) so both
    links should forward traffic.
    IP address on vlan and physical interface are different things. You need
    vlan 1 to push vtp between switches. This might get really complex. You
    should probably search for some good consultant which has experience
    with such setup.
    Ivan Ostres, Apr 18, 2005
  11. C Cant

    C Cant Guest

    another question about spanntree, what happens if you build up two 3550er
    you said it should work, because there 2 spanntrees (VL10 / VL20), but what
    about vlan 1? !! there would be aloop not?
    indeed i'm looking for one! or a way how to simulate my stuff.
    hmm, ok, lets take a look at this MPLS suggestion.....
    C Cant, Apr 18, 2005
  12. C Cant

    Ivan Ostres Guest

    No, in vlan 1 some ports would be blocked to keep out of loops.

    It's hard to find a good one...

    MPLS solution would not be feasible in your envirnoment. I've
    recommended is as a transport solution while I haven't seen "the
    picture", so I belive this solution is out.
    Ivan Ostres, Apr 19, 2005
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