4 x VOIP: Sipura-2000 behind Draytek 2900

I am close to sorting out 4 x VOIP for our household - but one snag
remains. I don't understand enough of how it all works to solve it from
first principles, and trial and error has not worked so far.

All four circuits are from sipgate.co.uk

I have two VOIP circuits on the 2900VG - these will call each other OK,
and work fine to and from PSTN.

I have two VOIP circuits on a Sipura-2000 [Hardware version 2.0.1(2401),
software 2.0.13(g)] which is connected to one of the LAN ports on the
2900 (call these 3 and 4). These will call each other OK, and work fine
to and from PSTN.

BUT calling between either of the 2900 circuits and either or the Sipura
circuits results in one-way audio only (ie Draytek can hear Sipura but
Sipura cannot hear Draytek).

The Draytek 2900VG has both circuits defined on SIP Port 5060 (but
changing second to 5061 seems to make no difference). I am running
firmware 2.5.6

The Sipura uses STUN (this and all other settings as recommended for
sipgate uk by the voxilla site). It has one circuit on Port 5060, the
other on 5061. Changing the second port to 5060 stops either circuit
working.

The Draytek has its DMZ set to the local Sipura IP address.

I do NOT have a fixed public IP address. (And, for what it is worth, I
am using PPPoE over a radio link rather than ADSL - the Draytek's WAN
port is connected to a D-link DWL-900 which handles the radio signal
from my ISP)

Is the one-way audio because I am missing a port translation for the
Sipura? If anyone knows the specific solution to my problem, that would
be wonderful. If not, is there any web resource that explains how SIP
uses ports for the non-propellor-head? And/Or any plain-english testing
resource that might help me find out what is wrong?

John Geddes
Derbyshire

 

yes, either port forwarding or open ports in firewall isse.

ISTR you need to have 5060, 5061, 5062, etc etc for multiple SIP
accounts.

The router won't need any forwarding by definition.

I have seen a suggestion that you should use 5060 5062 5064 etc but
I'm not clear if that was for multiple two-account devices.

Phil