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By SM23
#5294
Hi everyone,

I implemented a VOIP system in our office a few months ago, and no matter what I try I just cannot get it to work correctly.

We have problems with:
- Phones on call groups continuing to ring after one has been picked up (happens a lot). This has even culminated in us picking up one of the ringing phones to silence it and having the line continue to ring down the handset to us!
- Failure when trying to pick up another phone that is ringing.
- Delayed audio when picking up a call.
- BLFs working intermittently.
- Inability to transfer calls (a new, recent problem).

We don't actually have any problems with the quality of the calls, and when they connect then they seem robust and don't disconnect etc, but these others problems are seriously affecting our ability to trust the system.

Our hosted VOIP provider blames our router (Draytek 2830n) but another provider said that is the router they'd want us to have if we move to them so obviously it is capable. Or they blamed our managed switch, so we now have a HP 24 port unmanaged switch, with no change in the issues. The phones are Grandstream GXP2130's on the latest firmware, with one SNOM 320.

I am not an IT guy and have done what I can using Google, but now have reached the point where I think the only way to get this working correctly is to get a VOIP engineer in to try and optimise everything. If I google for one though I either get job adverts or VOIP companies who have engineers who will only help if you move your system over to them.

Does anyone have any recommendations for independent companies/engineers in the Midlands/Northamptonshire area that we could contact and get a quote from to look at our setup?

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By VoipIT
#5296
SM23 wrote:We have problems with:
- Phones on call groups continuing to ring after one has been picked up (happens a lot). This has even culminated in us picking up one of the ringing phones to silence it and having the line continue to ring down the handset to us!
- Failure when trying to pick up another phone that is ringing.
- Delayed audio when picking up a call.
- BLFs working intermittently.
- Inability to transfer calls (a new, recent problem).
A lot of issues there! :-/
SM23 wrote:Our hosted VOIP provider blames our router (Draytek 2830n)
Who are you using? It could be the Draytek router.
SM23 wrote:but another provider said that is the router they'd want us to have if we move to them so obviously it is capable.
Have you disabled SIP ALG on the router? Try making the following configuration changes:

Settings to change:
  1. Disable SIP ALG (SIP Application Layer Gateway' is used to try and avoid configuring Static NAT on a router. Its implementation, however, varies from one router to another, often making it difficult to inter-operate a router with SIP ALG enabled with a PBX. In general, you would want to disable SIP ALG and configure one to one port mapping on the router.)
  2. Allow traffic to/from the hosted VoIP providers IP addresses. (Ask them if your unsure of what these are)
  3. Update Firmware to latest version
  4. Untick "Accept large fragmented UDP packets" under the firewall configuration
SIP ALG
Issues such as one way audio, lack of incoming calls, registration issues and etc. can be due to SIP ALG

To disable SIP ALG you have to telnet into the router and enter the following commands.
  1. sys sip_alg 0 -- Disables sip alg
  2. sys commit -- Apply changes
  3. sys reboot -- Reboot router
Once the router is back online, reboot the IP phones or press re-register.

Incoming Call Problems
This is caused by a large IP SIP packet that is fragmented, but the router will not forward it. I understand that the new version will work if the checkbox under firewall -> general setup -> Accept large incoming fragmented UDP or ICMP packets is UNTICKED. This is the opposite to what you would expect.
SM23 wrote:Or they blamed our managed switch
It could be an issue but it's hard to say without without running some tests and looking over the logs.
SM23 wrote:so we now have a HP 24 port unmanaged switch, with no change in the issues.
Rules out the switch then.
CJT-80 liked this
User avatar
By SM23
#5301
Thank you for the reply voipIT.

Yes SIP ALG is the first thing our company mentioned, and the same thing they keep mentioning every time I go back to them! It is definitely off. To be sure about a month ago I turned it on, rebooted and turned it off then rebooted, just to be sure.

The configuration of the Draytek router is probably at fault, but the router itself is capable of high quality VOIP as shown by the other company that even sells them to go with their hosted VOIP solution.

I did have the large incoming packets option ticked so that has been unticked now thank you, I will see if that makes a difference, and I have requested the IP addresses off the company to add them into the

I am reluctant to add the name of the company here as the forum rules frown on that, so for now I will see what difference that makes, meanwhile I am getting quotes for different providers ready.
CJT-80, VoipIT liked this

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