IP Context Overview
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port. Therefore it is in your interest to decouple a logical interface from a physical port, by giving
names to interfaces that describe their usage and not the physical constitution.
As for any IP interface several IP related configuration parameters are necessary to define the
behaviour of such an interface. The most obvious parameters are the IP address and an IP netmask
that belongs to it.
For information and examples on how to create and configure an IP interface refer to Chapter 12, “IP
Interface Configuration” later in this user guide.
11.6 Configuring NAPT
Network Address Port Translation (NAPT), which is an extension to NAT, uses TCP/UDP ports in
addition to network addresses (IP addresses) to map multiple private network addresses to a single
outside address. Therefore NAPT allows small offices to save money by requiring only one official
outside IP address to connect several hosts via a SmartNode to the access network. Moreover NAPT
provides additional security, because the IP addresses of hosts attached via the SmartNode are made
invisible to the outside world. Configuring NAPT is done by creating a profile that is afterwards
used on an explicit IP interface. In the terminology of SmartWare an IP interface
uses
a NAPT profile,
as shown in Figure
For information and examples on how to configure Network Address Port Translation (NAPT) refer
to Chapter13, “NAPT Configuration” later in this user guide.
11.7 Configuring Static IP Routing
SmartWare allows defining static routing entries, which are table mappings established by the
network administrator prior to the beginning of routing. These mappings do not change unless the
network administrator alters them. Algorithms that use static routes are simple to design and work
well in environments in which network traffic is relatively predictable and where network design is
relatively simple.
For information and examples on how to configure static IP routing refer to Chapter 17, “Basic IP
Routing Configuration” later in this user guide.
11.8 Configuring RIP
The Routing Information Protocol (RIP) is a distance-vector protocol that uses hop count as its
metric. RIP is widely used for routing traffic in the global Internet and is an interior gateway protocol
(IGP), which means that it performs routing within a single autonomous system.
RIP sends routing-update messages at regular intervals and also when the network topology
changes. When a router receives a routing update that includes changes to an entry, it updates its
routing table to reflect the new route. The metric value for the path is increased by one, and the
sender is indicated as the next hop. RIP routers maintain only the best route (the route with the
lowest metric value) to a destination. After updating its routing table, the router immediately begins
transmitting routing updates to inform other network routers of the change. These updates are sent
independently of the regularly scheduled updates that RIP routers send.
RIP uses a single routing metric (hop count) to measure the distance between the source and a
destination network. Each hop in a path from source to destination is assigned a hop-count value,
which is typically 1. When a router receives a routing update that contains a new or changed
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