ELSA LANCOM Business 6000, Manual

Page: 119 / 174

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Technical basics
119
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ELSA LANCOM Business 6000
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EN
Example Inc. Since it is itself part of this division, it takes a closer look at
the address to find the name of the host. It then passes the packet on to
the host of the employee Sam 'Smith'.
Now we shall take a look at the example using proper IP addresses instead
of symbolic names. The network of Example Inc. has the numerical space
'192.168.100.0' to '192.168.100.255' at its disposal, with the '0' for the
network address and the '255' for the sender address.
The router has to remember that every address beginning with '192.168.100'
is located within the network of Example Inc.
Now imagine a router that is connected to the network of Example Inc.
through an interface. If it receives a packet with destination address
'192.168.100.4' and netmask '255.255.255.0', it will compare this with every
network address it knows. In doing so it carries out a logical AND with the
netmask, and compares the results with the network address: '192.168.100.4'
AND '255.255.255.0' is '192.168.100.0'. This is the network address of the
Example Inc. network. The router recognizes that the recipient is located
within Example Inc. and passes the packet on to the appropriate interface for
Example Inc. Within Example Inc. the packet is then passed on to the
appropriate subnet.
The same procedure is used for the transfer of IP packets within a network:
햲
If a host in the subnet of the development department wants to send a
data packet to Mr. Smith, the sender attaches the destination address
“Host Smith – Marketing – Example Inc.”.
햳
The router in the development division receives the packet and extracts
from the address the information that it is directed at the marketing
division of Example Inc. Since it is itself part of Example Inc., but not of
the marketing division, it passes the packet on to the router in the
superordinate network.
햴
The router in Example Inc. receives the packet and extracts from the
address the information that it is directed at Example Inc. Since it is itself
part of Example Inc., it takes a closer look at the address to find the name
of the division. It then passes the packet on to the router in the marketing
division, where the packet is passed on to the recipient.