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Chapter 4 - DSU RouteFinder Software
IP Setup
The IP Port Setup dialog box allows you change the IP routing capabilities that were established
during the software installation. This dialog box contains four tabs: Ethernet, WAN 1 (DSU), WAN
2, and Advanced.
The Unnumbered Link option can be selected (checked) for the WAN ports for point-to-point
links. When selected, it disables the Port Address and Remote Address groups. Unnumbered
links are useful only between two routers; in this case, local and remote. When running RIP over
a PPP link, both ends of the link must be either unnumbered or numbered with the same IP
subnet. An advantage of not assigning an IP address to each WAN port is that you conserve
valuable network and subnet numbers.
The Remote IP Address defines the IP address for the destination end of a point-to-point link and
is necessary only of the selected WAN port has been enabled for point-to-point operation. Note:
the remote IP address must fall within the same IP network as the local IP address.
The Frame Type option defines the MAC layer frame encapsulation to be used for IP
transmissions from the specified port. The Ethernet port supports Type II and SNAP frames, but
the WAN ports support only Type II frames.
In the Support group, ICMP Redirect defines if the specified port is permitted to issue an ICMP
Redirect message to the source IP address. The most likely cause of this message is the
delivery of a datagram to a router that is not on the forwarding path to the destination address.
This is often due to a wrong configuration of the IP client sending the datagram. The packet
causing the ICMP Redirect message to be transmitted is forwarded to the appropriate router.
ICMP Mask Reply enables support for nodes on the connected networks to learn their subnet
masks.
RIP enables RIP based routing on the specified port, and is normally enabled. However, RIP can
be disabled if you are using WAN links in Dial-on-Demand mode. In such links, disabling RIP will
reduce traffic on the link as this will also disable periodic RIP broadcasts. RIP routing on the port
will be automatically turned off when Dial-on-Demand is enabled in PPP port setup.
Finally, the RIP Poisoned Reverse option defines if Poisoned Reverse RIP messages are
supported on the specified port. Generation and processing of poisoned routes (RIP entries with
their respective metric set to 16 (defined as infinity) is enabled/disabled by this parameter.
Poisoned reverse is a method used by RIP to improve the rate of convergence of the routing
tables of interconnected IP routers. Routers supporting poisoned reverse that receive such RIPs
ignore the entries set to 16 and thus prevent the propagation of unnecessary (and often incorrect
MTASR2-201
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