Configure GRE interfaces
Digi TransPort User Guide 226
Advanced GRE parameters
Metric
The connected metric of an interface. The default metric of a connected interface is 1. By
allowing the interface to have a higher value (lower priority), static routes can take preference
to interfaces. For normal operation, leave this value unchanged.
MTU
The maximum transmission unit. In this text box you can enter the greatest amount of data
that can be transferred in one physical packet. The default value is 1400.
Tunnel Key
This parameter is normally used with multi GRE (mGRE). The tunnel key adds an extra field to
the GRE header where a key number can be applied. When used, incoming GRE packets must
have a matching tunnel key number to be accepted by this tunnel. When the Tunnel key
parameter is used the IP address parameter is not required.
Enable the firewall on this GRE tunnel
The Firewall parameter turns Firewall script processing on or off for this interface. If using the
firewall for problem detection on a tunnel interface, the interface to put OOS will need to be
specified, such as:
pass out break end on tun n from any to 100.100.100.29 port=4000 flags S!A inspect-state
oos ppp n 5
Enable GRE checksums
Selects whether to add GRE checksums to GRE packets when the router is terminating a GRE
tunnel. Set this parameter to off to disable checksums, and to on to enables checksums.