244
6620-3201
9.2 Multiple Subscriber Numbers
An MSN (multiple subscriber number), is an alternative number provided by the telephone service
provider which when dialled, will also route through to your ISDN line. It is possible to purchase
several MSN’s for an ISDN line. This means that in effect one ISDN line can have several ISDN
numbers.
Every entity in the router which is capable of answering an ISDN call (Adapt, LABP and PPP) has an
MSN parameter.
A protocol entity‘s MSN parameter can be used to:
♦
cause a protocol instance not to answer an incoming ISDN call (if the trailing digits of the ISDN
number called do not match the entry in this
fi
eld).
♦
increase the answering priority of an instance (if more than one protocol instance is con
fi
gured
to answer and the trailing digits of the ISDN number called match the value of the MSN parameter for
a particular protocol instance).
Example
Consider the following:
♦
an Adapt instance is bound to a serial port and ATS0 for that serial port is set to 1
♦
PPP instance 0
has answering turned On
♦
the ISDN line to which the router is connected has two numbers: the main
number is 123456
and the MSN number is 123789
Normally, because ADAPT has a higher answering priority than PPP, the Adapt instance will answer
when either of the numbers are called. However if the ISDN number dialled is 123456 and 456 is
entered into the MSN parameter of PPP then PPP will answer instead. This will also have the effect of
preventing PPP from answering if any other ISDN number (e.g. 123457) has been called.
This means that whenever 123456 is called the PPP instance will answer and that whenever 123789
is called the V120 instance will answer.
It is possible to connect multiple ISDN devices to the same ISDN line. MSN’s can then be used to
allow the different ISDN devices to be dialled individually (i.e. dial the main ISDN number and get
through to ISDN device one, dial the
fi
rst MSN and get through to ISDN device number two, dial the
second MSN and get through to ISDN device number three, etc.).
9.3 Multiple PPP Instances
It is also possible to con
fi
gure multiple instances of a particular entity to answer. For example, PPP
instance, 0, 1 and 4 could be con
fi
gured to answer. In this case provided that none of the PPP
instances are busy, the PPP instance with the highest number will answer
fi
rst. MSN’s can also be
used to ensure that a chosen PPP instance answers the call.
Multiple protocol entity answering instance rules:
ADAPT
The lowest free Adapt instance with auto-answering enabled will answer
fi
rst.
PPP
The lowest free PPP instance with answering on will answer
fi
rst.
LAPB
The lowest free LAPB instance with answering on will answer
fi
rst.
