Digi TransPort WR31 User Manual page 226

Configure network interfaces
Use IP Address:
A virtual host IP address for the local end of the tunnel, configured for routing purposes. This IP
address has no other use and needs no mask as it is a host address, such as 1.1.1.1. Normally,
use this option in conjunction with IPSec. Do not use this parameter if the interface is selected as
the source using the Use Interface options above.
Destination IP Address or Hostname
The FQDN or IP address of the remote end of the tunnel. This could also be the virtual host IP
address for the remote end of the tunnel, configured for routing purposes. such as 2.2.2.2.
Enable keepalives on this GRE tunnel
Enables or disables the GRE keepalive parameters. Keepalives are needed so allow the router to
determine whether the tunnel interface is receiving traffic correctly or not. If keepalives fail, the
tunnel is marked as down.
Send a keepalive every s seconds
When configured to a non-zero value, keepalive packets is sent to the remote end of the tunnel
and the response is monitored to detect if the tunnel is up or down. If the tunnel is detected as
down, the routing table metric will be altered. Value is configured in seconds. If this value is set
to 0, the router does not use keepalives.
Bring this GRE tunnel down after no replies to n keepalives
The consecutive number of keepalive packets that need to fail before the tunnel is detected as
being down.
Bring this GRE interface up to send keepalives
Whether or not the GRE keepalive packets will activate the tunnel. If set to YES and the tunnel
drops the GRE keepalive packet will try to raise the tunnel again. If set to NO and the tunnel has
been marked as down due to the GRE keepalives not being received, the router will only raise
the tunnel if a packet (other than a GRE keepalive) needs to be routed.
Digi TransPort WR Routers User Guide
Configure GRE interfaces
226