sundance-communications.com/forum Forums TDM Business Telephone Systems NEC Telephones & Systems DSX with SIP, dial out issues

Hi guys, I have a very inconsistent problem when dialing out, I would get a dial tone, dial a number and recieve a busy signal, but after 5-10 reattempts call will go thru. No one else was using phones. Never have any problems with incoming calls.
Girls at reception saying that it happens more often with toll free numbers and cell numbers than local, but I wasn't able to prove it during test.
Setup:
DSX80, VoIP board with 4 ports, Vitelity as sip trunk provider, 4 DIDs with up to 10 channels, 50/10 Comcast Internet, static ip, SMC business class modem/router with office server in DMZ and DSX thru port forwarding.
This is my first setup with VoIP board, everywhere else I use sip-fxo gateways, so I have nothing to compare with.
All ideas are very welcome
Thank you

Have you tried the 3.42.12 firmware? It seems to fix a lot of Sip trunk issues.

I believe 3.42.12 is a beta release.
I did update one nearby customer to 3.42.11, no issues so far, but he is on alnalog trunks, so no help there.
I will certainly try it before switching to sip gateway.
Thank you for advise.

VoIP board was very bad idea in the first place, why experiment with customer 80 miles away.... stupid me.

You have to upgrade with a compact flash to take advantage of the SIP enhancements.

I didn't know there is a difference. I used system administrator System>Update option from 3.42 to 3.42.12 However, It didnt solve dial out problem.
It also requires newer version of System Administrator software which I wasn't able to download, because link points to dealers forum and i dont have a login, tried to register multiple times in last 3 years, but no responce.
Anyway, I spoke with Vitelity today and they are saying that DSX is pointing to their inbound server and I have to add outbound proxy server as well, but DSX does not have an option for outbound server in Providers tab.
I guess sip gateway is the only option left

You have followed this guide

https://www.necdsx.com/docs/files/sip_trunking/dsx_and_vitelity_setup_1.01.pdf

Yes I did, except in version 3.42 interface of programm 1831/1832 looks different, instead of "Proxy Address" it's called "Domain Address" and I assumed that it's the same and entered outbound.vitelity.net (Vitelity proxy address), even if I leave it empty it doesnt make any difference. Every 5th outgoing call would still get a fast busy signal.
Inconsistency of the issues makes me think that it has nothing to do with settings or equipment.
Their IT tech supposed to install some software to monitor bandwidth, will see what he says.
Thank you ttech for trying to help

If you have 4 Ports and did not get additional license, Your channels 5-10 will not work.

You will need to buy 2 more 4 port licenses

Excuse my English, I didn't mean every 5th simultaneous call, I meant every 5th attempt to dial out would be unsuccessful. There is only 4 VoIP port but they never use more than 4 lines, and in case they do, we do have a 5th pots line for failover.
Today after speaking with Comcast tech we decide to get a block of 5 static IPs and instead of DMZ to server and port forwarding to DSX we assigned static IPs, also auto speed negotiation on LAN ports at comcast modem/switch was turned off and set to manual 100Mb full duplex (supposedly it could cause delays)
In 2 hours of intense testing on new setup not a single failed call. I really hope it will work.
I will update this post in few days.

Problem solved
IT tech says that problem was caused ether be double NAT or DSX DHCP with static IP.
One Issue solved, but bigger problems might be coming, since now DSX is on public IP and no firewall is present, i wonder how it will deal with DoS attacks. Least I could do is disable web admin port.
Thank you everyone.