Operation Manual

Operating modes and functions
ELSA LANCOM Wireless
41
English
How can you assist the workstation computer now?
By default, the router sends the computer a response with the address of the router
which knows the route to the destination network (this response is known as an ICMP
redirect). The workstation computer then accepts this address and sends the data packet
straight to the other router.
Certain computers, however, do not know how to handle ICMP redirects. To ensure that
the data packets reach their destination anyway, use local routing (in
ELSA LANconfig in
the 'TCP/IP' configuration section on the 'Router' tab or in the /
Setup/IP Router-
module/Local Routing On
menu). In this way you instruct the router itself in
your device to send the data packet to other routers. In addition, in this case no more
ICMP redirects will be sent.
This may seem to be a good idea in principle, but local routing should still only be used
as a last resort, since this function leads to doubling of the number of data packets being
sent to the destination network required. The data is first sent to the default router and
is then sent on from here to the router which is actually responsible in the local network.
Dynamic routing with IP RIP
In addition to the static routing table ELSA routers also have a dynamic routing table
containing up to 128 entries. Unlike the static table, you do not fill this out yourself, but
leave it to be dealt with by the router itself. It uses the Routing Information Protocol (RIP)
for this purpose. All devices that support RIP use this protocol to exchange information
on the available routes.
What information is propagated by IP RIP?
A router uses the IP RIP information to inform the other routers in the network of the
routes it finds in its own static table. The following entries are ignored in this process:
쮿
Rejected routes with the '0.0.0.0' router setting.
쮿
Routes referring to on other routers in the local network.
Which information does the router take from received IP RIP packets?
When the router receives such IP RIP packets, it incorporates them in its dynamic routing
table, which looks something like this:
IP address IP netmask Time Distance Router
192.168.120.0 255.255.255.0 1 2 192.168.110.1
192.168.130.0 255.255.255.0 5 3 192.168.110.2
192.168.140.0 255.255.255.0 1 5 192.168.110.3