Digi TransPort WR31 User Manual page 303

Configure network interfaces
if it has been idle for h hrs m mins s secs
The router deactivates the PPP instance after the time specified in these text boxes if it detects
that the link has not seen traffic.
Alternative idle timer for static routes s seconds
An alternative inactivity timeout for use in conjunction with the Make PPP n interface use the
alternative idle timeout when this route becomes available parameter on the Configuration
> Network > IP Routing/Forwarding > Static Routes > Routes n > Advanced web page. The
router uses this timeout until the PPP instance next deactivates only. After that, it uses the
normal timeout value.
If the link has not received any packets for s seconds
The amount of time the router waits without receiving any PPP packets before disconnecting.
The timer is reset with each received PPP packet.
if the negotiation is not complete in s seconds
The maximum time, in seconds, allowed for the PPP negotiation to complete. If negotiations
have not completed within this period, the interface is deactivated.
Enable NAT on this interface
When enabled, causes the router to apply Network Address Translation (NAT) to IP packets on
this interface. When enabled, the following additional parameters appear:
IP address/IP address and Port
These radio buttons select whether IP address translation only should be applied or whether
port number translation should also be applied to IP packets.
NAT Source IP address a.b.c.d
The IP address of the interface to use as the source address in IP packets crossing the NAT
interface.
Enable IPsec on this interface
When enabled, causes the router to use the IPsec protocol to secure the connection. Enabling
this setting displays the following additional parameters:
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.
Digi TransPort WR Routers User Guide
Configure Advanced interfaces settings: External modems and PPP
303