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Technical basics
ELSA MicroLink Cable
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There are two considerations when using these IP addresses:
The IP addresses used in a private network should not leave this network, i.e. an
Internet connection is only possible when using IP masquerading, for example.
The packets for these IP addresses will not be routed in the Internet, i.e. backbone
routers will simply reject such IP packets. Depending on the provider, serious
consequences may result if such IP packets are released on the Internet.
IP routing and hierarchical IP addressing
Routing
Every IP packet contains the IP addresses of the source and of the recipient. A router
receives IP packets at its interface, interprets the destination address and passes the
packets on to those interfaces that are nearest to the recipient. Finding the appropriate
path is called routing.
Routing-table
Every router manages a table (routing table). This table indicates the quickest interface
connection to the host for every host in the network. You can imagine that, as they grow,
these tables may exceed the capacity of the router—the Internet, as a worldwide linking
up of publicly accessible IP computers contains several millions of hosts.
Hierarchical IP
addresses
For this reason, hierarchical IP addresses were introduced. This means dividing the IP
network into subnets in which IP addresses are appointed from a coherent numerical
range. It is possible to establish several hierarchy levels, so that different subnets can
be merged. The principle is similar to the hierarchical address used by paper mail,
consisting of a country, a city, a street and a number.
The consequences of this hierarchical IP addressing:
Since all hosts within one network have the same network address, the host
address is sufficient for the hosts within this network to communicate with one
another.
A router has to know both the addresses of the hosts that are directly connected to
it, and the addresses of all networks and subnets that are reachable via adjacent
routers.
It is
not
necessary for a router to know
all
other possible IP addresses.