ip helper-address confusion

Discussion in 'Cisco' started by Northern Lights, Jul 24, 2003.

  1. I am relatively inexperienced with Cisco routing, so this is probably a
    simple question. Here's the hardware:

    Location A
    Cisco 2621 Router
    IOS 12.0
    Interfaces - e0 to local LAN
    s0/0.100-s0/0.105 to WAN (IP -

    Locations B-H
    Cisco 1720 or 1750
    IOS 12.0
    Interfaces - e0 to local LANs on each router
    s0/0.1 to WAN on each router (IP -

    This network is running 3DES on frame relay.

    Here's the problem:
    I am attempting to use a PC remote control software package (NetSupport) to
    control PCs on the network.
    The software resides at location A above. I am unable to see the PCs on the
    subnets at locations B thru H
    with the NetSupport software when browsing, but can see them using the
    client's IP address.

    NetSupport looks at the network broadcast address to find available clients.
    My thinking is that an ip helper-address
    command is needed for each subnet B-H on the router at location A. Also, I
    would need to use the
    ip forward-protocol 5405 command as the software uses udp port 5405 to talk
    to the clients.

    My questions:
    First, is my thinking correct on using the ip helper-address/ip
    forward-protocol commands?
    Next, would I use the ip helper-address command on e0 at location A? or
    another interface?
    Am I missing something else?

    As a test, I have tried using ip helper-address and on e0 at location A
    in conjunction with ip forward-protocol 5405 with no success.

    Can anyone help?


    If replying by e-mail, replace the nospam with an underscore character
    Northern Lights, Jul 24, 2003
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  2. On Thu, 24 Jul 2003 14:09:33 -0400, Northern Lights wrote:


    > As a test, I have tried using ip helper-address and
    > on e0 at location A
    > in conjunction with ip forward-protocol 5405 with no success.
    > and are the subnet broadcast addresses at
    locations B and C, I guess, so you need to ensure that you have "ip
    directed-broadcast" on inteface E0 at locations B and C.

    Without "ip directed-broadcast" the router will drop the packet when it
    sees that the destination address is the broadcast address.

    You can use "debug ip udp" at A to check the router is forwarding the
    packets as you expect.

    Martin Gallagher, Jul 25, 2003
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