Digi TransPort WR31 User Manual page 458

Configure Virtual Private Networking (VPN)
Advanced L2TP n parameters
Retransmit interval s milliseconds
The amount of time, in milliseconds, the router waits before retransmitting a Start Control
Connection Request (SCCRQ) frame. The default value of 250ms should be changed to a higher
value (say 4000ms) if L2TP is running over a GPRS link.
Retransmit count n
When using L2TP over GPRS or satellite networks, the first few packets are sometimes lost.
Setting the retransmit count in the text box to a higher value than the default of 5 will increase
reliability of the tunnel.
Layer 1 Interface Sync port n/ISDN
These radio buttons select the layer 1 (physical) interface to use to terminate the L2TP
connection. The available options are ISDN or one of the router's synchronous serial ports. When
Sync port n is selected, the sync port number is selected from the drop-down list.
Allow this L2TP tunnel to answer incoming ISDN calls
When enabled, the L2TP entity answers incoming ISDN calls.
MSN
The filter for the ISDN Multiple Subscriber Numbering (MSN). It is blank by default but when the
answering facility (above) is enabled, the router only answers ISDN calls where the trailing digits
match this MSN value. For example, setting the MSN value to 123 prevents the router from
answering calls from any calling number that does not end in 123. Not applicable when
answering is off.
Sub-address
The ISDN sub-address filter to use in conjunction with the ISDN answering function. When
answering is set to On and there is a valid sub-address in this text box, the router only answers
calls where the trailing digits of the calling sub-address match this sub-address. For example,
setting the sub-address value to 123 prevents the router from answering calls where the sub-
address does not end in 123.
Digi TransPort WR Routers User Guide
IPsec parameters
458