Can make outgoing calls but can't receive calls

[ReidTel]

I've got a customer that has SIP trunks on a IPO 9.0 Partner edition. They are saying that they can make outgoing calls but can't receive incoming calls. When you call their main number you hear the message that “you have reached a nonworking number. Announcement 14 switch 18-3.”. Their SIP provider is Allied and they are saying that there’s a routing issue with the PBX. They’re getting 503 service unavailable errors to their SBC. There have been no configuration changes so says the customer. I will be comparing the original cfg file saved to my laptop to their current cfg to make sure. The customer also said that now it seems they are able to receive calls for about 30 minutes and then it goes back down. This pattern repeats itself throughout the day. My questions are has anyone experienced this issue before and where do I begin to troubleshoot? I checked alarms and there are none. Strange. Thanks for any help you can give.



Larry Reid
Reid Telesys Communications
Fort Washington, Md

http://www.reidtel.com

 

[pmcook]

What are your settings under SIP URI for local URI, contact and name? Replace the values with a * and see what happens. The 30 minute timeout could be a DHCP lease issue.

 

[ReidTel]

The local URI is the customer's phone number. Where would I find the SIP URI? Would it be the same? Also before I make changes why would the issue occur if no changes have been made since the installation and it has been working for 5 months?

Larry Reid
Reid Telesys Communications
Fort Washington, Md

http://www.reidtel.com

 

[amriddle01]

SIP is very difficult to diagnose, you need a lot of knowledge of how it works on the IPO, you need to make lots of traces and test calls and then combine those things to make a best guess and then change that and test it, this also true of the SBC you are using, so double trouble. It's going to be difficult to give you an answer without this thread dragging on for several days/weeks I imagine

 

[ReidTel]

Well the customer needs to get this resolved so I need to start somewhere. If it takes days that's fine but the SIP provider has passed the buck to us and we can't pass it back to them unless we can prove it's not IPO. I was hoping someone here had that knowledge. I just need suggestions on where I can start checking.

Larry Reid
Reid Telesys Communications
Fort Washington, Md

http://www.reidtel.com

 

[amriddle01]

Comparing configs is probably unnecessary, check the audit trail from latest config you took.
You will need to use monitor and select the SIP filters then start tracing, wireshark can't hurt either, but as I said, if you don't know what you're looking for it going to be hard to work out (even if you do know it's extremely difficult)

 

[ReidTel]

Thanks for the information as well as the warning. Like 2 feet of snow wasn't enough for me to stress over lol.

Larry Reid
Reid Telesys Communications
Fort Washington, Md

http://www.reidtel.com

 

[derfloh]

If your side seems to be correct (from what you think) I suggest to ask the provider what he gets from you and what he really expects to get. With that info you can have a look at SysMon traces and the packet capture at the public side of the SBC.

Then there is a good chance to tune your setup to meet the provider's requirements.

 

[pmcook]

SIP URI is under the extension applet. Choose the URI and edit it. You will see a tab for SIP URI.

 

[DavidCT]

This sounds like classic firewall. Most of the time, firewall issues affect inbound more so than outbound.

What firewall is in use, and have you consulted with the person who provides support? The firewall can trace of the packers are being stopped at the firewall, or going through it.

Focus on the firewall.

 

[ReidTel]

The IPO is not on their network. SIP is connected directly to WAN/LAN port. What makes this strange is that calls come in successfully about 40-50% of the time. I am pumping calls through to them this morning on the half hour and so far no problems.

Larry Reid
Reid Telesys Communications

 

[amriddle01]

So the WAN/LAN port is directly connected to the internet? It has a routable address on the web?
Big mistake, they are probably getting hammered by loads of registration attempts from the Middle East and the Baltics, that can act like a DOS with SIP trunks causing all sorts of issues, and then they'll probably crack your passwords and cost you/your customer thousands in toll fraud

 

[ReidTel]

It's not connected directly to the internet. It's connected to Allied's router and another device that hands off the SIP to the IPO via their private internet. They provide the necessary security protection.

Larry Reid
Reid Telesys Communications

 

[ReidTel]

Ok after 4 successful inbound calls, the last 2 went to intercept saying "your call could not be completed as dialed...". Now I just made another call and the call completed successfully. This is crazy.

Larry Reid
Reid Telesys Communications

 

[amriddle01]

your call could not be completed as dialed...". That's not a system prompt, that's not reaching the system, I think your issue is carrier related, perhaps congestion on their uplink (seen it before wihen carriers run tight margins)

 

[ReidTel]

My thoughts exactly. They're insisting that it's the IPO. Now that I've heard it myself I will let them know.

Larry Reid
Reid Telesys Communications

 

[amriddle01]

If the trunk is down/returning fault messages when they try they may well play that message also, so it's no sure thing what it is, just another possible cause. But if it goes through their router and then another piece of equipment then there is a lot of scope for matters beyond your control put it that way