3Com 3C13636 Configuration Manual page 711

3Com Router 3000 Ethernet Family
Configuration Guide
The filter-policy import command allows a routing protocol to filter routes received
from the same routing protocol and to block the routing information filtered out from
being added to the routing table. This command, however, does not take effect on the
routes redistributed from other routing protocols, because those routing entries have
been added to the routing table before a blocking action can be taken.
The filtering performed by a link-state protocol is different from that performed by a
distance-vector protocol.
A link-state protocol can block routing information from being added to the routing table
but cannot filter LSAs. This, however, does not prevent the related LSAs from being
advertised to neighbors.
A distance-vector protocol, on the contrary, filters routing tables received from
neighbors and the routing information filtered out does not appear in the routing table.
III. Redistributing Routing Information Discovered by Other Routing Protocols
A routing protocol can redistribute the routes discovered by other routing protocols to
enrich its route information. When other protocol routing information is to be
redistributed, the route-policy can be used for route information filtering to implement
the purposeful redistribution. If the destination routing protocol redistributing the routes
cannot directly reference the route costs of the source routing protocol, you should
satisfy the requirement of the protocol by specifying a route cost for the redistributed
route.
Perform the following configuration in routing protocol view.
Table 7-3 Redistribute routes from other protocols
Set to redistribute routes from other
protocols
Cancel the setting for redistributing
routes of other protocols
By default, the routes discovered by other protocols will not be distributed.
Note:
In different routing protocol views, the parameter options are different. For details,
respectively refer to the import-route command in different protocols.
Operation
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7-5
Chapter 7 IP Routing Policy Configuration
Command
import-route protocol [ med med | cost
cost ] [ tag value ] [ type { 1 | 2 } ]
undo import-route protocol