Setting up an OBI110 and another ATA on the same LAN

[chetstone]

I have a 110 that's been working nicely with Google Voice. I just subscribed (I won't go into the reasons here) to a VOIP provider that requires you to use an ATA that they provide (a Linksys 2102).

I got the device and plugged it in and it configured itself immediately and it worked fine, until I tried to call a friend that uses the same VOIP provider, and he tried to call me. In either case, the phone rang, but when answered neither of us could hear the other.

I contacted the provider's support (after unplugging the OBI and testing again to make sure it wasn't interfering), and they said it's a NAT problem and I either need to put the 2102 in a DMZ (which I can't do) or forward a bunch of ports to the 2102.

My question is, if I open these ports, will it break the OBI?

Here's the list of ports they asked me to open:

Code Select Expand


Port:        53/udp
Port:        123/udp
Port:        80/tcp
Port:        sip.5060/udp
Port:        sip.5061/udp
Port:        rtp. range from 13456 to 13462/udp <-- please take note this is a range of ports.


[RonR]

You may only need to forward RTP ports.  I'd start with only these and see how it goes:

13456 - 13462  ->  Linksys 2102

16600 - 16998  -> OBi110

[chetstone]

Ron,

Thanks for your reply. Tried this and many other permutations of opening ports and DMZ working with the provider's support, to no avail. Turns out the problem is that our ISP does not allow direct connections between subscribers on the local network.

[Everton]

Huh?  Could you explain further?  How does the ISP block such communication?  Isn't the calls being routed through your VOIP provider, as oppose to direct IP dialing (ATA-to-ATA)?

Ron,

Thanks for your reply. Tried this and many other permutations of opening ports and DMZ working with the provider's support, to no avail. Turns out the problem is that our ISP does not allow direct connections between subscribers on the local network.

[chetstone]

Huh?  Could you explain further?  How does the ISP block such communication?  Isn't the calls being routed through your VOIP provider, as oppose to direct IP dialing (ATA-to-ATA)?

The SIP signaling is done via the VOiP provider, but once the connection is established, the actual media (voice packets) are sent direct ATA - to - ATA. Thus the phone would ring but when answered, no sound.

The probable explanation on why our ISP blocks these packets is here:

http://www.dslreports.com/forum/r26720709-connectivity-No-route-to-local-network-

[Stewart]

If your friend has a number in the US or Canada, you could avoid the problem by calling him from your GV line.

If that's inapplicable or undesirable, there is probably another workaround.  What country are you in?  ISP?  Modem make/model?  Separate router, if any?  Provider accessed via SPA2102?  Other providers, if any, configured in OBi?

[chetstone]

Thanks for the offer of help, Stewart, but this particular problem doesn't need to be solved. I can always pick up the landline and call my friend, it's a local call.

The reason for the test is that we are starting up a WISP to compete with our local ISP, who offers a top speed of a miserable 768k. (We're lucky to get half of that most of the time.)

We want to offer phone service to our customers, so we're evaluating wholesale VOiP providers.

This test was valuable. Now we know one potential problem that we can ask our networking gurus to avoid when architecting our system. I have a feeling our customers will be wanting to call their neighbors and will expect to hear each other!

By the way no matter what we did with regard to opening ports or not, DMZ or not, both the OBI and the 2102 always worked perfectly, coexisting nicely on my LAN, except for this one problem (which never went away, even when the OBI was completely removed).