ELSA LANCOM Business 6000, Руководство пользователя

Страница: 151 / 174

|
Technical basics
151
|
ELSA LANCOM Business 6000
|
EN
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 address and network mask identify the destination network, the distance
shows the number of routers between the transmitter and receiver, the last
column shows which router has revealed 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
automatically incremented when the corresponding amount of time has
elapsed. The distance is set to '16' after 3.5 minutes (route not reachable) and
the route is deleted after 5.5 minutes.
Now if the router receives an IP RIP packet, it must decide whether or not to
incorporate the route contained into its dynamic table. This is done as
follows:
The route is incorporated if it is not yet listed in the table (as long as there
is enough space in the table).
The route exists in the table with a time of '5' or '6'. The new route is then
used if it indicates the same or a better distance.
The route exists in the table with a time of '7' to '10' and thus has the
distance '16'. The new route will always be used.
The route exists in the table. The new route comes from the same router
which notified this route, but has a worse distance than the previous
entry. If a device notifies the degradation of its own static routing table
in this way (e.g. releasing a connection increases the distance from 1 to
IP address 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