Question Transparent Bridge and Firewall

  • Hello,

    I need to setup a transparent bridge. I found this in the forum
    Great read very easy to follow.

    Here is my situation-

    I have 100 meg fiber line with a Ethernet hand off. Currently my provider installed a Cisco ME3400 for the hand off. I was assigned a block of IP's
    77.x.x.x/30 but actually needed a class c.

    So I went ahead and ordered a class c. Now I have 2 separate IP blocks.

    WAN -> 77.x.x.x/30
    LAN -> 66.x.x.x/24

    I have to use the 77.x.x.x for the hand off to them. Is it possible to bridge the 2 different blocks together?

    Example -
    WAN <–> 77.x.x.x <--> 66.x.x.x

    I hope that makes sense.


  • You could have you ISP route the 66 network to one of your 77 addresses. This would be an ideal routed solution. You will need to disable nat. I would not bridge if I where you.

  • They told me that they assigned the 66 block to the same vlan as the 77 block.

    So if I just do a standard router setup.

    Wan - Static ip 77.x.x.x
    Lan - 66.x.x.x block using DHCP / and no Nat

    This should be ok?

    Really appreciate the help.


  • No. That I'd not sufficient. The ISP must route the 66 block to a 77 address. Otherwise you are going to have to bridge or perhaps proxy arp.

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