Dynamic Routes; Static Routes; Multiple Routes - 3Com 9000 SX User Manual

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Dynamic Routes

Dynamic routes are typically learned by way of RIP. Routers using RIP

exchange information in their routing tables in the form of RIP

advertisements. Using dynamic routes, the routing table contains only

networks that are reachable.

Dynamic routes are aged out of the table when a RIP update for the

network is not received for a period of time.

Static routes are manually entered into the routing table. Static routes

are used to reach networks not advertised by routers. You can

conﬁgure up to 64 static unicast routes on the Switch 9000.

Static routes can also be used for security reasons, to control which

routes you want advertised by the router. You can decide if you want

all static routes to be advertised by using the following command:

[enable | disable] rip exportstatic

The default setting is enabled. Static routes are never aged out of the

routing table.

When there are multiple, conﬂicting choices of a route to a particular

destination, the router picks the route with the longest matching

network mask. If these are still equal, the router picks the route using

the following criteria (in the order speciﬁed):

Directly attached network interfaces

ICMP redirects (refer to Table 8-4)

Static routes

RIP

Directly attached network interfaces that are not active.

You can also conﬁgure blackhole routes—trafﬁc to these destinations

is silently dropped.

Overview of IP Unicast Routing

8-3

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