3Com CoreBuilder 3500, Implementation Manual

Page: 432 / 592

432 C
HAPTER
15: IPX R
OUTING
RIP operates with active and passive network devices:
■
Active devices
— Usually routers, they broadcast their RIP messages
to all devices in a network; they update their own routing tables when
they receive a RIP message.
■
Passive devices — Usually hosts, they listen for RIP messages and
update their routing tables; they do not send RIP messages.
On your system, you select a RIP mode to determine how RIP operates, as
described in “IPX RIP Mode” later in this chapter.
An active router sends a RIP message every 60 seconds. This message
contains both the network number for each destination network and the
number of hops to reach it. In RIP, each router through which a packet
must travel through to reach a destination counts as one network
hop .
Routing Tables A routing table collects information about all intranetwork segments. This
table allows a router to send packets toward their destinations over the
best possible routes.
The table contains an entry for every network number that the router
knows about. The router uses this information when the router is not
directly connected to a packet’s destination network. The routing
information table provides the address of another router that
can forward
the packet toward its destination.
The routing table consists of the following elements:
■
Interface — The interface number of the router that is used to reach
a network segment
■
Address — The network segments that the router knows about
■
Hops to network — The number of routers that must be crossed to
reach a network segment
■
Tiks to network — An estimate of the time in seconds that is
necessary to reach a network segment
■
Node — The node address of the router that can forward packets to
each network segment. When the node is set to all 0s, the router is
directly connected.
■
Aging timer — The time in seconds since the network’s last update