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Operating modes and functions
ELSA MicroLink Cable
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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, the cable modem
will take this into account and include the poorer entry in its dynamic table.
The interaction of static and dynamic tables
The router uses the static and dynamic tables to calculate the actual IP routing table it
uses to determine the path for data packets. In doing so, it includes the routes from the
dynamic table which it does not know itself or which indicate a shorter distance than its
own (static) route with the routes from its own static table.
Local routing
You know the following behavior of a workstation within a local network: The computer
searches for a router to assist with transmitting a data packet to an IP address which is
not on its own LAN. This router is usually notified to the operating system by its property
of being the default router or gateway. It is often only possible to enter one default router
which is supposed to be able to reach all the IP addresses which are unknown to the
workstation computer if there are several routers in a network. Occasionally, however,
this default router cannot reach the destination network itself but does know another
router which can find this destination.
How else can you assist the workstation computer?
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