2 ip routing, 1 the ip routing table – Lancom Systems LCOS 3.50 User Manual

Page 66

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LANCOM Reference Manual LCOS 3.50

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Chapter 7: Routing and WAN connections

66

Routing and

W

A

N

con

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ections

Transmission of data packets
As soon as the connection is established, the router can send the data
packet to the Internet.

7.2

IP routing

An IP router works between networks which use TCP/IP as the network proto-
col. This only allows data transmissions to destination addresses entered in
the routing table. This section explains the structure of the IP routing table of
an LANCOM router, as well as the additional functions available to support IP
routing.

7.2.1

The IP routing table

The IP routing table is used to tell the router which remote station (which
other router or computer) it should send the data for particular IP addresses
or IP address ranges to. This type of entry is also known as a “route“ since it
is used to describe the path of the data packet. This procedure is also called
“static routing” since you make these entries yourself and they remain
unchanged until you either change or delete them yourself. Naturally,
“dynamic routing” also exists. The routers use the routes in this way to
exchange data between themselves and continually update it automatically.
The static routing table can hold up to 256 entries, the dynamic table can hold
128. The IP router looks at both tables when the IP RIP is activated.

You also use the IP routing table to tell the router the length of this route's
path so that it can select the most suitable route in conjunction with IP RIP
where there are several routes to the same destination. The default setting for
the distance to another router is 2, i.e. the router can be reached directly. All
devices which can be reached locally, such as other routers in the same LAN
or workstation computers connected via proxy ARP are entered with the dis-
tance 0. The “quality level” of this route will be reduced if the entry addressed
has a higher distance (up to 14). “Unfavourable” routes like this will only be
used if no other route to the remote station in question can be found.

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