[cisco-nas] AS5350XM in mixed VoIP and dialup environment

[Bernhard Schmidt]

Hi everyone,

I sent some of those questions to cisco-nsp already, but maybe this (or
at least for some parts cisco-voip) is the better forum.

we're currently evaluating two Cisco AS5350XM for use in our university
network. It should replace the old Ascend TNT boxes for ISDN/modem
dialup and provide a SIP/PSTN gateway to use for our VoIP PBX to be
installed next year. The whole setup will basically look like this

+----------------+
|      PSTN      |
+----------------+
  | | | | | |
  | | | | | | 6*E1
  | | | | | |
+----------------+     E1    +-------------+
|    AS5350XM    |-----------| channel box |
+----------------+           +-------------+
        +
        + SIP
        +
+----------------+
|   SIP PBX (*)  |
+----------------+

Current setup is just one E1 to our HiCom.

All six E1 lines will be configured the same way and will have a large
block as well as several additional numbers configured (so calls to one
number can be signalled on one random E1).

Data (ISDN) or Voice (modem) calls to several numbers on that trunk
should be handled by the box itself (ordinary PPP dialup). A small block
of our numbers should be sent to the channel box (so that is basically
PSTN-to-PSTN switching). An important thing here would be that PSTN to
the channel box is transparent regarding data, so we can connect any
device there. All remaining destinations should be sent to the PBX with
SIP.

My first question is regarding dialup. Currently we have the whole
dialup configuration on Serial3/0:15 and additionally on Group-Async0,
which has both 108port spes configured in (group-range 1/00 2/107). This
makes the Cisco answer each and every call it receives with PPP. If I
wanted to connect to different "configuration profiles" depending on the
dialed number, I had to put a "dialer pool-member x" on the lines and
use it in several Dialer-interfaces with the same "dialer pool x" and
different "dialer called <number>", correct? Would that work with async
(modem) connections as well? As far as I understood the documentation it
won't, and I would need to use resource-pooling to assign specific
numbers to specific async lines and then group those lines specifically.

The second question is about the use of the SPE dsps. We patched some
lesser used lines/numbers to the two Ciscos we got and the output of "sh
spe" does not look to good. E.g. at the moment we have 5 modem users (no
compression on the group-async and no multilink) and  6 digital users
(multilink and compression allowed), of which three are ordinary
dialups, two have multilink enabled but only one channel in use and one
has two channels. Still, show spe shows

Ports     : Total  216  In-use    61  Free   155  Disabled     0
Calls     : Modem    5  Digital    0  Voice    0  Fax-relay    0

the box has two NP108 and one 8E1, but if it uses 61 DSP lines on 11
calls we won't be remotely able to fill the lines. Does active just mean
"powered because it was used at some time" or is it used to an incoming
call can't use it anymore?

We run IOS 12.4(1c) as preinstalled on the boxes.

Regards,
Bernhard