Kas susidures, kokios praktikos, kaip ten su IP adresais. Kiekvienam VOIP 
aparatui isoriniu IP adresu nesinoretu pirkti...
Yra stotele su voip ir 5 voip telefonai. Skambinti skambina, bet nera garso. 
Problemos aprasymas:

"The Trouble with NAT and VOIP
In addition, the way in which conventional VoIP protocols are designed is 
also posing a problem to VoIP traffic passing through NAT. Conventional VoIP 
protocols only deal with the signalling of a telephone connection. The audio 
traffic is handled by another protocol and to make matters worse, the port 
on which the audio traffic is sent is random. The NAT router may be able to 
handle the signalling traffic, but it has no way of knowing that the audio 
traffic is related to the signalling and should hence be passed to the same 
device the signalling traffic is passed to. As a result, the audio traffic 
is not translated properly between the address spaces.

At first, for both the calling and the called party everything will appear 
just fine. The called party will see the calling party's Caller ID and the 
telephone will ring while the calling party will hear a ringing feedback 
tone at the other end. When the called party picks up the telephone, both 
the ringing and the associated ringing feedback tone at the other end will 
stop as one would expect. However, the calling party will not hear the 
called party (one way audio) and the called party may not hear the calling 
party either (no audio).

The issue of NAT Traversal is a major problem for the widespread deployment 
of VOIP. Yet, the issue is non-trivial and there are no simple solutions. In 
general terms there are two ways to deal with this problem:

avoid the problem altogether
working around the problem"
http://www.voip-info.org/wiki/view/NAT+and+VOIP

Jei butu tik vienas voip aparatas, tuomet puiku. Idedi I DMZ ir tiek ziniu, 
bet ju yra daugiau.