[VoiceOps] Screwy DSL modem NAT troubles

Carlos Alcantar carlos at race.com
Tue Feb 22 01:19:07 EST 2011


Linksys ALG seems to break everything sip on the firewall side sonicwall seems to be the death of sip.


Carlos Alcantar
Race Communications / Race Team Member 
101 Haskins Way, So. San Francisco, CA. 94080
Phone: +1 415 376 3314  Fax:  +1 650 246 8901 / carlos *at* race.com / www.race.com



-----Original Message-----
From: voiceops-bounces at voiceops.org [mailto:voiceops-bounces at voiceops.org] On Behalf Of Carlos Alvarez
Sent: Monday, February 21, 2011 3:08 PM
Cc: voiceops
Subject: Re: [VoiceOps] Screwy DSL modem NAT troubles

We go through this all the time with Qwest DSL customers.  Unfortunately I don't have model numbers for you, we stopped documenting things when we noticed that they have all new modems every few months.  However we've had success with having the customer call Qwest and tell them they want to run VoIP phones, the Qwest reps seem to know that as a trigger and send a compatible modem.  I do recall that the best ones are Netopia, and we've had good support when we engage them directly via chat.

We also find that modems start going bad slowly after a couple years, and VoIP is the first to get impacted, of course.



Matthew S. Crocker wrote:
> Has anyone else noticed that the latest batch of DSL modems have broken NAT when it comes to VoIP?   I'm seeing stable VoIP customer get broken when the DSL modem is swapped out.  The modem NATs the phones to modem IP port 5060.  So, 10 phones behind the router become one phone to the SBC.  A race condition occurs and phones go in and out of service at random.  It looks like the router is trying to do a SIP ALG but very very broken.
>
> Do anyone have a DSL modem/router they use that works well with VoIP?
>


-- 
Carlos Alvarez
TelEvolve
602-889-3003


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