The ROUTED program, which does RIP for 4.2BSD systems,
has many options. One of the most frequently used is:
"routed -q" (quiet mode) which means listen to RIP infor-
mation but never broadcast it. This would be used by a
machine on a network with multiple RIP speaking gate-
ways. It allows the host to determine which gateway is
best (hopwise) to use to reach a distant network. (Of
course you might want to have a default gateway to
prevent having to pass all the addresses known to the
Internet around with RIP).
There are two ways to insert static routes into "routed",
the "/etc/gateways" file and the "route add" command.
Static routes are useful if you know how to reach a
distant network, but you are not receiving that route
using RIP. For the most part the "route add" command is
preferable to use. The reason for this is that the
command adds the route to that machine's routing table
but does not export it through RIP. The "/etc/gateways"
file takes precedence over any routing information
received through a RIP update. It is also broadcast as
fact in RIP updates produced by the host without question,
so if a mistake is made in the "/etc/gateways" file,
that mistake will soon permeate the RIP space and
may bring the network to its knees.
One of the problems with "routed" is that you have very
little control over what gets broadcast and what
doesn't. Many times in larger networks where various
parts of the network are under different administrative
controls, you would like to pass on through RIP only nets
which you receive from RIP and you know are reasonable.
This prevents people from adding IP addresses to
the network which may be illegal and you being
responsible for passing them on to the Internet. This
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type of reasonability checks are not available with "routed"
and leave it usable, but inadequate for large networks.