[asterisk-users] Asterisk NAT

Chris Bagnall asterisk at lists.minotaur.cc
Wed Feb 19 02:38:29 CST 2014

On 19/2/14 4:53 am, Gholamreza Sabery wrote:
> Hello, a few days ago I sent a question:
> http://lists.digium.com/pipermail/asterisk-users/2014-February/282241.html
> but no one answered me! I just want to know is it possible or not?

I can't help on the "can Asterisk detect they're behind the same NAT" 
part of the question, but I would caution you that an assumption that 
'each NAT box has a single external IP' is risky - especially if you 
have to deal with the possibility of double-NAT and other such evilness 
(and it's hard to avoid sometimes - how many non-tech people go and buy 
a wireless router to 'extend their WiFi' rather than an access point, or 
don't know how to switch said router into AP-only mode).

You also have to consider users who have multiple LANs (which might not 
necessarily be able to route between themselves) behind a single 
external IP: this one's quite common in shared/managed office 
environments - one external IP and several RFC1918 VLANs internally, 
with no routing between them.

So in summary, unless you have a considerable level of control over your 
endpoints such that you can be sure these (and no doubt other) scenarios 
don't apply, it's probably safest to send RTP traffic through Asterisk 
regardless, otherwise you're potentially opening up a support nightmare 
for yourself.

Kind regards,

This email is made from 100% recycled electrons

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