Discussion in 'VOIP' started by Edmond, Jul 3, 2003.

  1. Edmond

    Edmond Guest

    I have a 3Com NBX 100 with a VoIP license. I enabled IP-on-the-fly
    for the system to allow phones to work over ethernet (layer 2 only)
    locally and IP remotely. System software is version 4.1.21.

    I placed a phone on a remote user's home network. The network is a
    Comcast cable modem plus a LinkSys router using NAT to 192.168.1/24.
    I programmed the 3Com phone to have a static IP on that private
    subnet, then told the router to make that IP the DMZ host (i.e. every
    inbound connection is forwarded to this private IP). The phone
    connects to the Call Processor, reboots, then never comes online. It
    just shows the MAC address and the twirling "/" forever. Unfortunely
    the phone will not even connect if it uses the IP address assigned to
    the cable modem, because the phone does not support DHCP and Comcast
    does not support static IP addresses. The phone works fine when
    plugged in to the LAN that the Call Processor is on.

    No matter what I plug in for the network settings on the phone, it
    seams the Ping utility in the Program memu complains about either
    "Dest not found" or "Bad My IP." Has anyone configured an NBX phone
    with VoIP on a shared cable modem and gotten it to work?


    Edmond, Jul 3, 2003
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  2. Edmond

    Delphi Guest

    Check 3com knowledgebase solution ID 2.0.72651549.3219280


    Best regards,
    Delphi, Jul 4, 2003
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  3. Edmond

    Edmond Guest

    Thanks for the pointer. For those who can't see the Knowledge Base
    article below (you must have a 3Com NBX under warranty to view it):

    The article confirms my suspicion that the call processor receives a
    connection from the initiating phone, and retrieves its IP address
    settings stored in the phone's flash - the same settings used to reach
    the call processor. This information is then passed to the other NBX
    phone or line card connecting to the outside phone network, which
    attempts to connect directly to this IP address. With a nonpublic IP
    address, you will connect to the call processor, but the call
    processor will attempt to connect to that IP address rather than the
    originating IP address.

    Bottom line: If you want your cable modem or DSL users to use VoIP
    with a 3Com NBX system, you will want to find a provider that offers
    multiple static IP addresses cheaply. Otherwise you might want to
    consider the Cisco 7900 series IP Phones.

    Edmond, Jul 8, 2003
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