Digi TransPort WR31 User Manual page 255

Configure network interfaces
Enable IPsec on this interface
When enabled, causes the router to encrypt traffic on this interface using the IPsec protocol. The
following two additional configuration parameters are revealed when this box is checked.
Keep Security Associations (SAs) when this PSTN interface is disconnected
When enabled, causes the router to maintain (such as not flush) the SA when the interface
becomes disconnected. The normal behavior is to remove the SAs when the interface becomes
disconnected.
Use interface x,y for the source IP address of IPsec packets
If it is required to use another interface (such as not the interface currently being configured) as
the source address for IPsec packets, this may be achieved by selecting the desired interface
from the drop-down list and typing the desired interface instance number into the adjacent text
box.
Enable the firewall on this interface
When enabled, applies the firewall rules to traffic using this interface.
Digi TransPort WR Routers User Guide
Configure PSTN interfaces
255