Many 802.1q tagged vlans, 1 Cisco 2621 router

Discussion in 'Cisco' started by justin.krejci, Nov 14, 2005.

  1. I am having a difficult time understanding what I need. Here is the
    network (yes I have installed a nm-1e into the 2621 to get 3 lan

    tagged vlans ---- fa0/0 #Cisco router# fa0/1 ---- tagged vlans
    eth1/0 (internet)

    Cisco eth 1/0 has (default gateway is

    cisco fasteth0/0 has, physically there are about 45 tagged
    VLANs coming over this interface, hosts using the subnet

    cisco fasteth0/1 has, physically there are about 45 tagged
    VLANs coming over this interface, hosts using the subnet

    Basically I need to be able to get all 90 tagged vlans to be able to
    talk on to internet

    I think I need to use bridge-group for this, will this config do what i
    need or do I need to add eth1/0 to the bridge-group 1 as well? Or
    something completely different?

    int fa0/0
    bridge-group 1
    interface fa0/1
    bridge-group 1
    bridge 1 protocol ieee
    justin.krejci, Nov 14, 2005
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  2. Let me clarify a couple of points too. The switches are NOT cisco (no
    ISL) but do support 802.1q tagging. I basically want the FE ports on
    the router to allow any traffic no matter want tagged VLAN they are
    coming from and all hosts and VLANs talking to FE0/0 are coming from
    the same IP subnet, and likewise all hosts and VLANs talking to FE0/1
    are coming from their own subnet.

    Is this possible? I have IOS Version 12.2(31) w/feature set IP/Plus. I
    don't need to have one VLAN to be able to talk to another VLAN, at
    least not right now, I am more in need of getting the VLANs to be able
    to talk to the internet. Ideally I would like to use different more
    capable switches, but that is not a possibility right now.
    justin.krejci, Nov 14, 2005
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  3. justin.krejci

    MC Guest

    will need to configure subinterfaces, one for each VLAN you need.
    On each sub interface will set encapuslation to dot1q

    for example:

    interface ethernet 0/0.100
    encapuslation dot1q 100

    Just repeat the aboce for each VLAN needed, the subinterface number can
    be any number but I chose the same as the VLAN ID. the number at the end
    of the encapsulation command must be the VLAN ID.

    Make sure that 801.q1 tagging is set on the port of the switch that the
    router is connected, setup switch VLANs.

    MC, Nov 16, 2005
  4. Thank you for the reply. I had already tried that but it did not work.
    Hosts on the VLAN were not able to talk to the IP address on the
    physical interface. The work around I have done is add 1,000 lines of
    config to the router (good thing from scripting languages like perl) to
    setup all of the sub interfaces (1 for each VLAN) and the DHCP server
    pools (1 for each VLAN). So I am just using a class C address block for
    each VLAN but since they are all NAT'ed I can use up as many as I want.

    So I have a whole of lines that are similar to this

    ip dhcp pool vlan149
    dns-server X.X.X.X Y.Y.Y.Y

    interface FastEthernet0/1.149
    encapsulation dot1Q 149
    ip address
    no cdp enable

    With the large config and only 32K of NVRAM I also had to enable config
    compression so it would all fit in NVRAM. This is done via this config

    service compress-config
    justin.krejci, Dec 5, 2005
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