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Operating modes and functions
ELSA MicroLink Cable
34
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. This protocol is used by all devices with RIP to exchange information
regarding the reachable 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:
Rejected routes with the '0.0.0.0' router setting.
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:
What do the entries mean?
IP addresses and network masks identify the destination network, the distance indicates
the number of routers between sender and receiver, the final column indicates the router
which announced this route. This leaves the 'Time'. The dynamic table thus shows how
old the relevant route is. The value in this column acts as a multiplier for the intervals at
which the RIP packets arrive. A '1', therefore, stands for 30 seconds, a '5' for about 2.5
minutes and so on. New information arriving about a route is, of course, designated as
directly reachable and is given the time setting '1'. The value in this column is
192.168.0.0 255.255.0.0 0.0.0.0 0 Excludes transmission of all data
packets to networks using private
address spaces.
172.16.0.0 255.255.0.0 0.0.0.0 0
10.0.0.0 255.0.0.0 0.0.0.0 0
224.0.0.0 224.0.0.0 0.0.0.0 0
255.255.255.255 0.0.0.0 CABLE 1 All data packets which cannot be
allocated to the entries listed
above are transmitted into the
cable network.
IP address IP netmask Router name Dist. This is what happens:
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