[asterisk-users] No audio on Zap (T1/PRI) channels

[Steve Totaro]

Steve Edwards wrote:
> On Thu, 4 Oct 2007, Matthew Fredrickson wrote:
>
>   
>> Steve Totaro wrote:
>>     
>>> Steve Edwards wrote:
>>>       
>>>> I have 12 T1's going into 3 servers, 4 in each into "Digium, Inc. Wildcard
>>>> TE410P Quad-Span togglable E1/T1/J1 card 3.3v (rev 02)" cards.
>>>>
>>>> Each "group" of T1's have the primary D on 24 and the secondary D on 96.
>>>>
>>>> The first server (ts20) and the last server (ts22) can playback
>>>> "demo-congrats" fine. The "middle" server (ts21) cannot -- just dead air.
>>>>
>>>> If I call via ZAP, dead air. If I call via IAX, I hear the file.
>>>>
>>>> I copied /etc/zaptel.conf, /etc/asterisk/*,
>>>> /var/lib/asterisk/sounds/demo-congrats.gsm from ts20 to ts21 -- no joy.
>>>>
>>>> I have seen this in my system log file:
>>>>
>>>> Oct 2 18:41:49 WARNING[7477]: chan_zap.c:8087 zt_pri_error: [Span 0
>>>> D-Channel 0] PRI: !! Got reject for frame 95, but we have nothing --
>>>> resetting!
>>>>
>>>> I'm running asterisk-1.2.24, asterisk-addons-1.2.7, libpri-1.2.5,
>>>> zaptel-1.2.20.1.
>>>>
>>>> "show channel zap/?," "zap show channel ?" appear identical between
>>>> working and non-working systems both "on-hook" and "off-hook."
>>>>
>>>> Any clues or clues where to start looking?
>>>>         
>>> Double check both zaptel.conf and zapata.conf and also call the telco to
>>> make sure they have they have the same NFAS scheme on all T1s setup
>>> correctly.  Sometimes (let's face it, alot of times, the provider messes
>>> something up).
>>>
>>> Also check that all of your T1 cables are plugged into the correct T1
>>> port.  I have made that mistake myself when doing 28 T1s off a T3.  I
>>> got dead air just as you described.
>>>       
>> Yes, if you are running NFAS, getting dead air on a call is a symptom of
>> not having the logical span identifier correctly corresponding to the
>> physical span you have plugged in (spanmap option in zapata.conf, IIRC).
>>     
>
> Success (finally). The spanmap that worked (of no value to anyone else) 
> is:
>
>          trunkgroup                      = 1,96,24
>          spanmap                         = 1,1,1
>          spanmap                         = 2,1,3
>          spanmap                         = 3,1,2
>          spanmap                         = 4,1,0
>
> We were told (by Qwest) that the primary D channel was the 24th channel on 
> the first T1 and the secondary D channel was on the 24th channel on the 
> second T1. This turned out to be false. We even had the tech drop carrier 
> on each T1 (one at a time) so we could identify which T1 was plugged into 
> which port on the card.
>
> The "winning" strategy was to configure all 4 T1's as if they had a D 
> channel and let Asterisk tell me which T1's actually had a "provisioned 
> and up" D channel using the "pri show span x" command. The one that showed 
> as "active" I made primary and "standby" as backup.
>
> Once I knew which physical channels were actually D's, setting up the 
> trunkgroup was easy.
>
> When I placed a call, I got audio. I nearly fell off my chair. Then the 
> next call was dead air. The first call landed on the last channel of a T1 
> and the next call was the first channel of the next T1.
>
> I tried to "logically" figure out which zapspan was which logicalspan, but 
> in the end I cracked open a beer, made a table of the 26 permutations and 
> stepped through them one by one. On my 13th try, I got an "order" that 
> gave audio on all 96 channels.
>
> The morals of the story:
>
> ) Don't believe the tech if it conflicts with reality.
>
> ) Don't accept an NFAS trunk group until you have tested each and every 
> channel.
>
> Thanks in advance,
> ------------------------------------------------------------------------
> Steve Edwards      sedwards at sedwards.com      Voice: +1-760-468-3867 PST
> Newline                                             Fax: +1-760-731-3000
>   
Steve,

Glad to hear you got it working! I love that feeling when you are so 
frustrated you just want to quit or smash something and then suddenly 
you succeed!

I like your troubleshooting strategy too, configure them all as if they 
had a D chan and the ones that come up are in fact Ds. So simple, yet I 
probably would not have thought of it. I would have just tried each 
configuration until it worked.

You should update the wiki with your little nugget of troubleshooting 
NFAS wisdom.

Congrats,
Steve Totaro