~ I realize that a PRI circuit contains 23B+1D channels. When
~ configuring this type of interface on a router, I believe the serial
~ interface is generated after configuring the "pri-group timeslots
~ 1-24" command (i.e. under controller T1 1/0). So, the following
~ interface is now available for configuration
~ "interface Serial1/0:23". I know that the ":23" is the D channel, but
~ is this representation only to signify that this serial interface is
~ indeed a PRI.
~ Although I know it works, it looks misleading when you see an IP
~ address configured for "int s1/0:23" when in essence it's the D
~ channel. You see this when there is typically only one dialer profile
~ configured in contrast to multiple "int DialerX" interfaces used with
~ dialer pools.
~ Just curious,
Your curiosity is perspicacious. Indeed, the semantics of our ISDN
D channel interfaces are rather recondite, and have confused even
some of our development engineers.
SOME commands that are entered on the D channel interface are
actually applicable to the D channel itself, and not to the
applications running on the B channels. For the most part,
these commands are prefixed with "isdn".
But MOST of the commands on the D channel interface are NOT
applicable to the D channel. Rather, the D channel interface
is used as a kind of legacy dialer (a la "dialer rotary-group")
via which the sync data calls are configured. For example,
"encapsulation ppp" on the D channel doesn't actually mean
that PPP is used on the D channel (which would be absurd as
D channels always use LAP-D encapsulation), but rather that
the *B* channels would use PPP.