Digi TransPort WR31 User Manual page 151

Configure network interfaces
Max Tx rate
On models with multiple Ethernet interfaces, this parameter specifies a maximum data rate in
kbps that the router will transmit on this interface. This may be useful in applications where
separate Ethernet interfaces are allocated to separate LANs and it is necessary to prioritize
traffic from one LAN over another.
TCP transmit buffer size
When set to a non-zero value, this parameter sets the TCP buffer size of transmitted packets in
bytes. This is useful for slow / lossy connections such as satellite. Setting this buffer to a low
value will prevent the amount of unacknowledged data from getting too high. If retransmits are
required, a smaller TX buffer helps prevent retransmits flooding the connection.
Take this interface out of service after n seconds when the link is lost
(such as cable removed or broken)
The length of time, in seconds, the router will wait after detecting that an Ethernet cable has
been removed before routes that were using that interface are marked as out of service. If the
parameter is set to 0, the feature is disabled such as routes using the interface will not be
marked as out of service if the cable is removed.
Enable NAT on this interface
Selects whether the Ethernet interface uses IP Network Address Translation (NAT) or Network
Address and Port Translation (NAPT) When the parameter is disabled, no NAT occurs. When
enabled, extra options are displayed, described below.
NAT and NAPT can have many uses, but the router generally uses them to allow a number of
private IP hosts (PCs for example) to connect to the Internet through a single shared public IP
address. This has two main advantages: it saves on IP address space (the ISP only need assign
you one IP address), and it isolates the private IP hosts from the Internet (effectively providing a
simple firewall because unsolicited traffic from the Internet cannot be routed directly to the
private IP hosts.
To use NAT or NAPT correctly in the example of connecting private hosts to the Internet, NAT or
NAPT should be enabled on the router's WAN side interface and should be disabled on the
router's LAN side interface.
Digi TransPort WR Routers User Guide
Configure Ethernet interfaces
151