Voici la solution : RTFM

Reports - asterisk log donne:
[2016-09-23 16:43:01] VERBOSE[11591][C-0000000c] sig_analog.c: -- Starting simple switch on 'DAHDI/3-1'
[2016-09-23 16:43:02] VERBOSE[11591][C-0000000c] pbx.c: -- Executing [s@from-analog:1] NoOp("DAHDI/3-1", "Entering from-dahdi with DID == ") in new stack
[2016-09-23 16:43:02] VERBOSE[11591][C-0000000c] pbx.c: -- Executing [s@from-analog:2] Ringing("DAHDI/3-1", "") in new stack

donc le system ne passe pas le DID.

En fouillant sur internet je trouve:
http://wiki.freepbx.org/display/FPG/...)+Channel+DIDs qui nous explique que :

What is the DAHDI Channel DIDs module used for?
The DAHDI Channel DIDs module allows you to assign a DID or phone number to specific analog channels.
Unlike SIP or PRI trunks, analog lines do not send a DID or dialed number to the PBX. Since the PBX routes all inbound calls based on the DID or number dialed, we need to map each analog port or channel to a fake number so we can match that number to an Inbound Route number and route your calls.
Each channel can be mapped to the same phone number if you want all calls on the analog lines to go to the same destination. This would be a common scenario if you have multiple POTS lines that are on a hunt group from your provider.
You MUST assign the channel's context to from-analog for these settings to have effect. It will be a line that looks like: context = from-analog in your chan_dahdi.conf configuration affecting the specified channel(s). Once you have assigned DIDs, you can use standard Inbound Routes with the specified DIDs to route your calls.

Donc les lignes analogiques ne passent pas le DID il faut utiliser :
Connectivity - DAHDI channel DIDs

On configure les ports FXO pour qu'ils passent le DID que l'on veut et on l'utilise ensuite dans les inbound route.
Voila