Inalp Networks SmartWare Release 2.10, Software Configuration Manual

Page: 88 / 357

88 IP Context Overview
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 Chapter
13 , “ 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
“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
destination-network entry, the router adds one to the metric value indicated in the update and enters
the network in the routing table. The IP address of the sender is used as the next hop.
RIP prevents routing loops from continuing indefinitely by implementing a limit on the number of
hops allowed in a path from the source to a destination. The maximum number of hops in a path is
15. If a router receives a routing update that contains a new or changed entry, and if increasing the
metric value by one causes the metric to be infinity (that is, 16), the network destination is considered
unreachable.
For information and examples on how to configure Routing Information Protocol (RIP) refer to
Chapter
RIP Configuration ” later in this user guide.
11.9 Configuring Access Control Lists
Packet filtering helps to control packet movement through the network. Such control can help to
limit network traffic and to restrict network use by certain users or devices. To permit or deny
packets from crossing specified interfaces, SmartWare provides access control lists.
An access control list is a sequential collection of permit and deny conditions that apply to packets
on a certain interface. Access control lists can be configured for all routed network protocols (IP,
11-1.
17,
18, “
Software Configuration Guide Release 2.10, Revision 1.00