Outbound calls "All circuits are busy"


Have been using the Grandstream phones and UCM for just over a year now, and for most part just had minimal issues. However just recently my remote location has been having issues with calling outbound with 2 of the phones. That location is using a UCM6202, with 13 GS phones, but I am told that 2 of them are not able to dial outbound. They can call extensions and can receive phone calls, just can’t dial out. I have already tried restoring the UCM from a “good” backup, I have updated all to latest FW, I have factory reset users phone, I have deleted his extension from UCM, and reconfigured new. Done this all and still not working.


check the permissions on those extensions


All are set to local, with local given permission to call outbound



Check to see if the IP address is on the Fail2Ban list?


I haven’t checked, but don’t think that is it. I have 11 other phones that are all tied to same UCM and they all seem to be able to call out. I am just confirming with my remote location.


Different post @mbrenneman you had said the following:

Under Maintenance -> Network Troubleshooting.

It’s a packet capture. You’ll need software like WireShark to view the results.



So for my issue with the outbound call, would I be looking at “ethernet capture” or “trace route”?

I have never used the network troubleshooting.


ethernet capture

I am not an expert by any stretch like the others here. I know how to make the capture but I’m not often sure what I’m looking at when I open up the file in WireShark. WireShark does have filters that allow you to look at telephony, for example, as opposed to all traffic through the device.


if you are sure that the outgoing routes are correct and the permissions are correct, there must be a problem, otherwise it would work.
1 - take a swphone and register it instead of one of the phones
a - it works -> the problem is located on the phone
b- does not work -> the problem is located on UCM

2 - create a new test extension and register the swphone and make sure everything works, then register the phones that don’t work today one at a time and see immediately where the problem lies

keep in mind that among the various hypotheses there could also be the dial plan of the two wrong phones.
First format the 2 phones and reconfigure them, make sure you have the last FW on both UCM and phones.
Good job.


Easiest part is voip call from Telephone, then you find you try and use flow sequence.
This will show you how call was done and what reply you get.
Then you can check error reply and compare with sip responses
https://en.wikipedia.org/wiki/List_of_SIP_response_codes for general idea what is wrong.

If there is no call in capture then it go worse and i think you need ask for advice or help (as there was no call flow at all).


If they can make calls between extensions and the like, then they are not banned.
How did you provision the phones? If via zero-config and the phones were working before, then you may be able to factory reset the phones and then let them re-config from ZC and see. I suppose it possible that some folks got curious and played with phone and may have altered some settings such as a dial plan, DTMF or other.

You can also possibly look in the CDR records and see the issue. Perhaps the extension owners are new and they are trying to dial a local number and no one ever bothered to tell them they needed to dial 10 or 11 digits. You could add a rule where you prepend the a 1 and area code for local calling so they can use 7 digit dialing.

Lacking that a network capture.


I don’t know what swphone refers to, but would be interested to try.


I did the provision through the UCM via zero-config, and yes all phones were working up until last week. Interestingly, I have had this issue before and just swapped a different users GX2135 phone for another and it worked. But to happen again to a different user seems odd. So my gut instinct is that the phones themselves are the issue, but just don’t know where to search. I plan on doing a network capture today, but not sure what I will be looking for.

As for users playing around, no one has access to the webGUI, but not saying that they didn’t try and play with the settings on the phones themselves, but I highly doubt that.

Yes I think I will be doing a network capture, but again I do not know what I am going to be looking for. As I have never done one before.


So it appears the issue is affecting more phones than what I initially knew. Out of 13 GS phones, 5 of them are affected. It also appears to have started happening as of Thursday (Jan 9th). But nothing was changed, and prior all were working properly.


you can try Zoiper (there is a version for Android and Windows) or the android IOS app of Grandstream -> GS Wave

Anyway, I’m guessing you did the tests I recommended above and gave me some feedback.


Fragmented packet issue. Removed excess codecs and all is working.