[cisco-nas] isdn and voice dialin config

[Mark Johnson]

At 02:13 PM 8/19/2004 -0500, James Sneeringer wrote:
>I've been tasked with migrating our only PRI (T1) off our last remaining
>Lucent PortMaster 3 and onto an existing Cisco 3640.  The PRI primarily
>handles "nailed up" 2b 128k MLPPP connections, but also handles the
>occasional modem dialup.  The 3640 will be equipped with an NM-1CT1-DSU
>and an NM-24DM, and is running c3640-is-mz.122-19.
>
>Since the modules are not yet installed, and since I don't have a spare
>PRI, I have no means with which to test this, so the eventual cutover
>will be "hot" and has to work correctly the first time.  This is the
>base config I've come up with to accomodate our requirements:
>
>     controller T1 2/0
>      pri-group timeslots 1-24

You also need to configure (either globally or under the interfadce) an
ISDN switch-type.

>     interface Loopback0
>      ip address X.X.X.1 255.255.255.255
>     !
>     interface Serial2/0:23
>      no ip address
>      dialer rotary-group 1
>      isdn incoming-voice modem
>     !
>     interface Group-Async1
>      no ip address
>      dialer rotary-group 1
>      async mode interactive
>      group-range 65 88
>     !
>     interface Dialer1
>      ip unnumbered Loopback0
>      encapsulation ppp
>      dialer in-band
>      dialer-group 5
>      peer default ip address pool dialin-pool
>      ppp authentication pap
>      ppp multilink

Since you say that the ISDN users are nailed up, and the modems users are
occasional, I would suggest you use different dialers.  For the ISDN users
you could use <dialer idle 0>, to effectively make the idle infinite.  You
would also then have more granularity in configuring async users (who may
not need/want MPPP) versus sync users.

Note too that the async users don't have to use DDR; the most immediate
reason to use DDR is to be able to define an idle timer and what is/is not
interesting in terms of traffic resetting the idle timer.  If you aren't
interested in either of these factors, then you don't need to employ DDR
for the async users.

>     ip local pool dialin-pool X.X.X.2 X.X.X.9

You would want, at most, 23 addresses available, possibly less given MPPP.

>     dialer-list 5 protocol ip permit
>     !
>     line 65 88
>      modem inout
>      transport input all
>      autoselect during-login
>      autoselect ppp
>
>Do I understand this correctly?
>
>   * Data calls will be directed to the Dialer interface by the
>     "rotary-group" statement on Serial2/0:23.

Yes, although there's no reason that the config could not be placed
directly under the PRI.  Using dialer-rotary is mostly for convenience,
in not having to configure multiple interfaces repetitively.  The
Dialer interface does not really have anything to do with any particular
call; it's more just a configuration repository for the physical interface(s).

>   * Voice calls will be directed to a modem by "incoming-voice" statement on
>     Serial2/0:23, and from there handled by the Group-Async interface based
>     on the "group-range" statement.  Calls are then handed off to the Dialer
>     interface by the "rotary-group" statement on Group-Async1.

Again, not really handed off to the dialer; they will terminate on the tty.

>   * Channels in use will appear in the form of Serial2/0:xx, where xx is the
>     actual channel used.

Yes.

>   * Data calls will appear on a Virtual-Access interface.

Only when MPPP is actually negotiated; and in that case, 2 serial B-channels
will be included as members in the Virtual-Access bundle master (sh ppp mult).

>   * Voice calls will appear on an Async interface corresponding to the TTY
>     they landed on.

Yes, assuming that MPPP is NOT negotiated (which is why you may want to
have a separate dialer interface for the async users, without MPPP enabled).

mark