Bay Networks 5390, Administering, Page: 264 / 888

A12-6 893-741-B
Internet Protocol (IP) Routing
• If the routes are both dial-out or both non-dial-out, the route with the highest metric is moved
to the cache.
• If the routes are both dial-out or both non-dial-out and have the same metric, the route with the
preferred interface type is stored in the routing table and the other in the cache. For example,
en0 routes are preferred over serial interface routes.
Routing Table
The RIP portion of the routing table contains routes for all IP destinations the Model 5390 server
can reach currently. This includes the local loopback route and the user-configured default route (if
one exists), as well as routes copied from the route cache, routes learned by RIP, and routes to
directly connected networks. The latter are called
interface routes and are discussed in Interface
Routes on page A12-9.
If a route becomes invalid (because its hop count reaches 16 or the interface to its next hop goes
down), it is kept for two minutes in the routing table, so that the route’s invalidity is advertised to
other routers (when active RIP is enabled).
RIP uses the routing table for the updates it advertises (when active RIP is enabled).
How Hosts Learn Routing Information
Unlike routers, hosts do not run routing applications and do not maintain extensive routing tables.
Host table entries tend to be restricted to information learned via ICMP messages generated by
routers on the network. When the Model 5390 server is acting as a router, it generates messages to
provide hosts with the following information:
• Whether or not the Model 5390 server is available as a router on the host’s local network.
• Whether or not the Model 5390 server knows of a better first hop than itself to a given
destination.
NOTE:
To display the route cache, use the netstat –C command
described in Displaying the route cache on page A12-67.
NOTE:
To display the routing table, use the netstat –r command
described in Displaying Routing Information on page A12-62.