Digi TransPort WR31 User Manual page 302

Configure network interfaces
Secondary DNS server
The IP address of the secondary DNS server that the remote peer should use when making DNS
requests, should the primary server be unavailable.
Request packet data connection
When enabled, causes the PPP instances to request a connection for sending a data packet.
Allow the PPP interface to answer incoming calls
When enabled, causes the PPP instance to answer an incoming call.
Only allow calling numbers ending with n
When set to answer calls, this setting provides a filter for ISDN sub-addresses. This value is blank
by default but when the PPP instance is set to answer calls, only numbers having trailing digits
that match the sub-address value in this test will be answered. So for example, if this value is set
to 123, only calls from numbers with trailing digits that match this value will be answered, for
example, 01942 605123.
Close the PPP connection after s seconds
The maximum time that the link will remain active in any one session. After this time, the link will
be deactivated.
if it has been up for m minutes in a day
The router deactivates the PPP instance after it has been active for the value specified in this
text box.
Digi TransPort WR Routers User Guide
Configure Advanced interfaces settings: External modems and PPP
302