Multiple subnets from single router?

Discussion in 'Cisco' started by Ned Trilby, Jul 29, 2004.

  1. Ned Trilby

    Ned Trilby Guest

    My ISP has allocated me this range (example) of addresses:
    ISP Subnet 123.123.123.0 255.255.255.240
    ISP Router Ethernet 123.123.123.1

    Cust#1 Ethernet 123.123.123.2
    Cust#1 LAN 123.123.123.16 252.255.255.240

    Cust#2 Ethernet 123.123.123.3
    Cust#2 LAN 123.123.123.32 255.255.255.240

    Cust#3 Ethernet 123.123.123.4
    Cust#3 LAN 123.123.123.48 255.255.255.240

    Cust#4 Ethernet 123.123.123.5
    Cust#4 LAN 123.123.123.64 255.255.255.240

    and so on for remainder of subnet. I want to run different customer
    networks from my site. The ISP has static routes for each subnet
    pointing to the "Ethernet" address e.g. he will route anything for the
    123.123.123.32 network to 123.123.123.3.

    I originally hoped to create VLANs on a CAT5500 switch with RSM and
    give the
    RSM VLAN interfaces the "Ethernet" address. But I cannot have more
    than one of
    these "ethernet" addresses on a single router as they are all in the
    same subnet (123.123.123.0 /28)
    I then thought of a single router with multiple ethernet interfaces -
    but I still have the same problem.
    I have a solution where I can put the ISP ethernet connection into a
    hub - then have multiple routers each with two ethernets - one for the
    ISP subnet,the other for the downstream "customer" subnet.
    This will work but will need a router for each customer - is there any
    other way I can achieve a working solution without having to get a
    router for each subnet?
    TIA,Ned
     
    Ned Trilby, Jul 29, 2004
    #1
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  2. Ned Trilby

    PES Guest

    I would explain the scenario to the ISP. They should want to make simpler
    (for you and them). However if they won't agree to a solution (routing to
    one address), you could use secondary addresses on a router. I'm not sure,
    but think this should also work on the rsm. Also, I'm not sure what the
    maximum number of secondary ip addresses is.

    On a router use
    int eth x
    ip address 123.123.123.2 255.255.255.240
    ip address 123.123.123.3 255.255.255.240 sec
    ip address 123.123.123.4 255.255.255.240 sec
     
    PES, Jul 29, 2004
    #2
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