3Com NBX + NAT DMZ
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?
Re: 3Com NBX + NAT DMZ
> 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?
Check 3com knowledgebase solution ID 2.0.72651549.3219280
Re: 3Com NBX + NAT DMZ
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.
"Delphi" <firstname.lastname@example.org> wrote in message news:<email@example.com>.. .
> > 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?
> Check 3com knowledgebase solution ID 2.0.72651549.3219280
> Best regards,
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