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Vlan to extend over wan frame relay link

Posted on 2004-11-02
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Last Modified: 2012-06-21


Hi

Here is a scenario:

I want to make a group of users to test Exchange 2003, some of the users are in London and some in Scotland, We have 1mb connection over frame relay in between the two sites.

I want to create a vlan and have both sites's users to be in that one vlan (same subnet). Is this possible and what would be the effect of this on my bandwidth ?


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Question by:kamal73
    14 Comments
     
    LVL 43

    Expert Comment

    by:JFrederick29
    VLAN information will not be carried over your Frame Relay circuit but you could create two seperate subnets on each side of the link for the test group.  Do they really need to be in the same subnet?  You could use bridging if so but I wouldn't.  I'd simply create a subnet different from the "production" LAN in London and Scotland and have routing take care of communication over the link.  You could then use ACL's to block communication between the production and test LAN's.

    For Example:

    10.1.0.0 (production LAN)London---------FR------------Scotland(production LAN) 10.2.0.0
                                             |                                    |
    192.168.1.0/24 (test LAN)---|                                    |----(test LAN) 192.168.2.0/24
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    Author Comment

    by:kamal73

    which kind of wan connection would allow vlan traffic on it. I thought vlan's whole purpose was to have no physical boundries and be able to have your selected clients to be connected to same segment.
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    LVL 43

    Expert Comment

    by:JFrederick29
    An ethernet WAN circuit could carry VLAN information end to end.  When I say VLAN information, I mean the 802.1Q tag to seperate the VLAN's.
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    Author Comment

    by:kamal73
    So if you want to connect two countries to same vlan, what kind of technolgy would you use then ?
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    LVL 79

    Expert Comment

    by:lrmoore
    VLAN and VLAN tagging has only the physical boundaries of the switched LAN. You can be thousands of miles apart, with fiber Ethernet connectivity and still have the same vlan on both ends. The boundary is the router that connects to the T1 circuit. When you have different media translation/encapsulation (Ethernet packets encapsulated into frame-relay), the vlan tags get stripped off and are not carried with the packets across the frame-relay..
    Layer 2 VLAN's are for switched LANS (no matter how big they are), and layer 3 routing is for WANS.
    You can use the router to bridge the LAN and WAN interfaces at both ends and you  can then have the same subnet on both sides, but bridging is not recommended unless you absolutely, positively have no other option.
    If you use VLAN 1 on both sides, and bridge the connection, then theoretically, all VLAN 1 hosts on both sides are in the same VLAN, but the VLAN tagging still does not propogate across the WAN.

    I guess you could fake it with any 1 VLAN if you use vlan tagging and subinterfaces on the routers:

    VLAN 1 - Interface Fast 0/0                                              Interface Fast 0/1 - VLAN 1
    VLAN 2 - Interface Fast 0/0.2 -- bridged to WAN link --------Interface Fast 0/1.1 - VLAN 2
    VLAN 3 - Interface Fast 0/0.3                                            Interface Fast 0/0.2 - VLAN 3

    You can bridge only one VLAN across the WAN link because the WAN link cannot be a trunk
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    Author Comment

    by:kamal73
    why is bridging of ethernet and wan connection not recomended ? What is the command to enable ethernet and serial port bridging.
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    LVL 11

    Expert Comment

    by:PennGwyn
    > which kind of wan connection would allow vlan traffic on it.

    We use an ATM LANE (LAN Emulation) backbone and an ATM WAN link between campuses, and are able to configure VLANs that span across the link.  We keep that to the absolute minimum, though, because carrying LAN broadcast traffic across a WAN link is a *really* bad idea.

    > I thought vlan's whole purpose was to have no physical boundries and be able to have your selected clients to be connected
    > to same segment.

    FEWER physical boundaries.  "NO physical boundaries" is a fantasy.

    0
     

    Author Comment

    by:kamal73
    why is bridging of ethernet and wan connection not recomended ?
    0
     
    LVL 43

    Expert Comment

    by:JFrederick29
    Because it should only be used when you are using a protocol that can not be routed.  If you are using a routed protocol like IP, then you should let it route between offices.  Why not set your test network up how I described?  Having a seperate test network is essentially doing the same thing...  
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    Author Comment

    by:kamal73
    In the test network we are also implementing microsoft clustering and for that we need to have all servers in the same subnet.
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    Author Comment

    by:kamal73
    any more comments from experts
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    LVL 79

    Expert Comment

    by:lrmoore
    What kind of routers do you have?
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    Author Comment

    by:kamal73
    I am sure we have a 7200.
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    LVL 79

    Accepted Solution

    by:
    Then try this on both ends, bridging the VLAN interface to the appropriate serial interface connecting to the other side

    !
    bridge 1 protocol ieee
    !
    !- VLAN 2 interface for example
    interface FastEthernet 0/1.2
      bridge-group 1
    !
    interface Serial 0/1.3
      bridge-group 1
    !

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