[asterisk-users] Doubling up; redunancy with DUNDi

[Gavin Hamill]

Hi :) We currently have a single * box with 4-port E1 card terminating
60 channels:

 [PSTN]
  |  |   2 x E1
[Asterisk]
  |  |   2 x E1
[Legacy PBX]


What I'd like to have is this:

[PSTN]
 | \______
 |        |
[*1]- - - -[*2] - DUNDi peering between 2 * boxes
 |        |
[Legacy PBX]

Whereby a call in either direction would be routed either 'straight
through' to/from the PSTN from/to the Legacy PBX, or in the case where
all channels were in use (we max out at about 40-45 channels usage), it
would connect via IAX to a free channel on the other * box.

This is slightly different from the DUNDi tutorials I have found on the
web (including markster's excellent one on voip-magazine.com) whereby
DUNDi is only consulted if 'is this extension local?' fails. In my
case, both sets of extensions are local to both boxes, but I want to
utilise any spare capacity on the other machine. Also, I am not using
any SIP devices here, only Zaptel ones.

Should this be as straightforward as replacing our current 'Dial'
entries in extensions.conf :

exten => _31.,1,Dial(Zap/G2/${EXTEN})

with a 'DUNDi-aware' version like:

exten => _31.,1,Dial(Zap/G2/${EXTEN})
switch => DUNDi/priv

How does this deal gracefully with the scenario of 'no free channels' ?

Is there much variance in DUNDi between 1.2.X and 1.4.X ?

Cheers,
Gavin.