NetComm V85 - Manual (Page 46)

46 V85 Desktop VoIP Phone User Guide
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In this example, the user configured the V85 to send SIP messages from port 5999 and RTP packets
from port 20000, which are same port numbers configured in NB620W.
Figure D-4
Note: The V85 needs a range UDP ports (RTP base port to RTP base port+6);
the RTP port specified (port 20000) in the V85 is the RTP base port so its
RTP range is 20000 ~ 20006.