Remote VLANs bridging over metro ethernet ...

Discussion in 'Cisco' started by Pedro Ribeiro, Jul 20, 2004.

  1. I have a problem to solve in the network design i'm doing for our
    campuses across the city.

    The WAN/MAN operator we are using have made us a good price for the
    links at 10 and 100Mbit/s from the data/comm center to every school,
    the circuits are terminated in 10BaseT/100BaseTX in the remote sides
    and in 1000BaseT in the main site with the circuits arriving each in
    his 802.1q VLAN. (In the remote side the frames are delivered
    untagged).

    The problem is that i need to pass VLANs across this links (Our VLANs
    over the Operator VLANs) and the Operator imposes several restrictions
    to traffic in the circuits:
    The maximum frame size allowed: 1500 bytes.
    Each circuit can only introduce 4 MAC addresses in each side.

    I can't use IEEE802.1q over these circuits because:
    - Maximum ethernet frames sent by machines (can't control MTU of
    them) after adding the VLAN tag will be oversized frames in the
    operators view and wil be discarded.
    - Each machine will introduce his MAC violating again, now the MAC
    limit.

    ISL could solve this last problem because frames are tunneled between
    switches point2point but the maximum frame size problem becomes bigger
    as the ISL introduces big overhead in encapsulation.

    Does anyone know any device (or IOS feature) that could transport
    VLANs across these circuits? (Some kind of remote bridge doing
    fragmentation & reassembly)

    TIA.
     
    Pedro Ribeiro, Jul 20, 2004
    #1
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  2. Pedro Ribeiro

    Ivan Ostres Guest

    In article <>, pribeiro-
    says...
    > I have a problem to solve in the network design i'm doing for our
    > campuses across the city.
    >
    > The WAN/MAN operator we are using have made us a good price for the
    > links at 10 and 100Mbit/s from the data/comm center to every school,
    > the circuits are terminated in 10BaseT/100BaseTX in the remote sides
    > and in 1000BaseT in the main site with the circuits arriving each in
    > his 802.1q VLAN. (In the remote side the frames are delivered
    > untagged).
    >
    > The problem is that i need to pass VLANs across this links (Our VLANs
    > over the Operator VLANs) and the Operator imposes several restrictions
    > to traffic in the circuits:
    > The maximum frame size allowed: 1500 bytes.
    > Each circuit can only introduce 4 MAC addresses in each side.
    >
    > I can't use IEEE802.1q over these circuits because:
    > - Maximum ethernet frames sent by machines (can't control MTU of
    > them) after adding the VLAN tag will be oversized frames in the
    > operators view and wil be discarded.
    > - Each machine will introduce his MAC violating again, now the MAC
    > limit.
    >
    > ISL could solve this last problem because frames are tunneled between
    > switches point2point but the maximum frame size problem becomes bigger
    > as the ISL introduces big overhead in encapsulation.
    >
    > Does anyone know any device (or IOS feature) that could transport
    > VLANs across these circuits? (Some kind of remote bridge doing
    > fragmentation & reassembly)
    >
    > TIA.
    >


    Well, the only method I've ever seen (at networkers) is QinQ. That is
    using dot1q inside of a dot1q.

    Does this mean that you have a flat L2 network without routers on any
    end?

    --
    -Ivan.

    *** Use Rot13 to see my eMail address ***
     
    Ivan Ostres, Jul 20, 2004
    #2
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  3. Yes, L2 flat, but I can't use QinQ or ISLinQ because I have the frame
    size and MAC limitations imposed by the operator ...

    Ivan Ostres <> wrote in message >

    ....

    > Well, the only method I've ever seen (at networkers) is QinQ. That is
    > using dot1q inside of a dot1q.
    >
    > Does this mean that you have a flat L2 network without routers on any
    > end?
     
    Pedro Ribeiro, Jul 20, 2004
    #3
  4. Pedro Ribeiro

    Gordon Smith Guest

    "Ivan Ostres" <> wrote in message
    news:...
    >
    > Well, the only method I've ever seen (at networkers) is QinQ. That is
    > using dot1q inside of a dot1q.
    >
    > Does this mean that you have a flat L2 network without routers on any
    > end?
    >
    > --
    > -Ivan.
    >


    Well... dare I say it :)
    Juniper routers have a feature called CCC (circuit cross-connect) that
    allows you to bridge layer 2 over layer 3 very well. Quite useful in a
    meshed & routed core network. It doesn't scale particularly well though, in
    terms of the number of CCC's you can run.

    Doing some form of bridging would keep the MAC count down across the
    provider's links.
    Unless their provider is running jumbo frames internally, delivering tagged
    circuits will reduce the MTU of the payload anyway, although that shouldn't
    be a real problem. There's a number of ways to get around that...
     
    Gordon Smith, Jul 20, 2004
    #4
  5. Hi,

    Are you realy sure you need to pass your vlans over the operators vlans?
    This is almost impossible (without spending huge amounts on specialized
    equipment capable of handling the throughput and resulting in complex
    setups). Example: setup an expensive router on either side, create a tunnel
    setup over the operator's vlans (l2tp, gre, ....) and bridge local traffic
    from local ethernet ports to the tunnels.

    If you're not sure, I would suggest going the other way and create a routed
    setup using layer-3 switches at either side of the link. (3550/3570 series?)

    Erik

    "Pedro Ribeiro" <> wrote in message
    news:...
    > I have a problem to solve in the network design i'm doing for our
    > campuses across the city.
    >
    > The WAN/MAN operator we are using have made us a good price for the
    > links at 10 and 100Mbit/s from the data/comm center to every school,
    > the circuits are terminated in 10BaseT/100BaseTX in the remote sides
    > and in 1000BaseT in the main site with the circuits arriving each in
    > his 802.1q VLAN. (In the remote side the frames are delivered
    > untagged).
    >
    > The problem is that i need to pass VLANs across this links (Our VLANs
    > over the Operator VLANs) and the Operator imposes several restrictions
    > to traffic in the circuits:
    > The maximum frame size allowed: 1500 bytes.
    > Each circuit can only introduce 4 MAC addresses in each side.
    >
    > I can't use IEEE802.1q over these circuits because:
    > - Maximum ethernet frames sent by machines (can't control MTU of
    > them) after adding the VLAN tag will be oversized frames in the
    > operators view and wil be discarded.
    > - Each machine will introduce his MAC violating again, now the MAC
    > limit.
    >
    > ISL could solve this last problem because frames are tunneled between
    > switches point2point but the maximum frame size problem becomes bigger
    > as the ISL introduces big overhead in encapsulation.
    >
    > Does anyone know any device (or IOS feature) that could transport
    > VLANs across these circuits? (Some kind of remote bridge doing
    > fragmentation & reassembly)
    >
    > TIA.
     
    Erik Tamminga, Jul 21, 2004
    #5
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