SOLVED Phones not working on specific ISP

[Raymond Burress]

Hi,

I am having some very odd issues with a very basic phone setup and was hoping someone could maybe help shed some light on things.

The setup is just a 4 phone build, very basic, one ring group that rings all 4 phones when calls come inbound (other setup as well, but nothing major). The customer is switching their internet provider to a new provider. If the system is on the old provider, which is a slow DSL connection and a basic dlink router they have, everything works without issue. As soon as I switch the provider to a new business cable connection (using modem in bridge mode and same router that works on other provider) calls cannot be answered. I also tried switching the modem out of bridge mode and letting it do the routing and still the same. If I call in, the exts all ring, if I answer from any of the phones you cannot hear anything and all the phones continue to ring, including the one that I just answered from. It will not call between phones or anything.

I was thinking maybe some kind of NAT issue, but the same router setup the same way is being used. As soon as I switch things back to the old provider, everything immediately starts working correctly again. Even ifI leave one of the phones on the old provider and put the other 3 on the new provider, the one phones works correctly and the other 3 do not.

I do not understand how it could be anything but an issue with the provider, but before going to them and having them investigate further I wanted to see if anyone else has seen/resolved similar issue before.

Oh, also, the phones are Grandstream GXP2130 phones.

Thanks

 

[FSM]

My English is very bad. sorry. I'm using translate.

I have not been able to answer my questions for a while.

I think your problem

Advanced/Access controls/domains add new provider.

 

[Raymond Burress]

Hi, Thanks for taking the time to answer.

The new provider I am referring to is just a new ISP, not a new SIP provider. This is a new ISP just on a client side. I wouldn't need to add this in Access Controls would I?

Thanks

 

[ad5ou]

Your problem is some sort of NAT issue. sngrep and/or sip trace on phones should show what exactly is happening.

A fix that might help is changing the Grandstreams to use "random port" for SIP.
<!-- # Use Random Port. 0 - No, 1 - Yes. Default is 0 -->
<!-- # Number: 0, 1 -->
<!-- # Mandatory -->
<P78>1</P78>

 

[Raymond Burress]

Thanks @ad5ou I was thinking it was some kind of NAT issue. But the router itself handles the NAT right? It just seems very odd that using the same router (not changing config at all) if I have everything on the old ISP it is perfect, switch to the new ISP with their modem in bridge mode and same router and it just falls apart.

Would the new ISP be controlling NAT somewhere on their side outside of the router?

I am not at the site right now so I will have to go over later and try the random port and check on a SIP trace.

Thanks

 

[ad5ou]

It isn't common if the modem is truly in bridge mode, but some ISP's have odd setups. I've seen a few cable modem/routers that still had firewall and SIP ALG settings even when in bridge mode.

 

[Raymond Burress]

Just an update on this. I had the new ISP come and swap the modem to a basic modem instead of going through their gateway in bride mode. Everything working great after they swapped the modem.

Thanks