C
HAPTER
45
| IP Routing Commands
Open Shortest Path First (OSPFv2)
– 1053 –
words, the cost of the route from any router within the AS is equal to
the cost associated with reaching the advertising ASBR, plus the cost of
the external route. When a Type 2 LSA is received by a router, it only
uses the external route metric to determine route cost.
â—† A tag can be used to distinguish between routes learned from different
external autonomous systems (other routing protocols). For example, if
there are two ASBRs in a routing domain: A and B. ASBR A can be
configured to redistribute routes learned from RIP domain 1 (identified
by tag 1) and ASBR B can redistribute routes learned from RIP domain
2 (identified by tag 2).
EXAMPLE
This example redistributes routes learned from RIP as Type 1 external
routes.
Console(config-router)#redistribute rip metric-type 1
Console(config-router)#
RELATED COMMANDS
default-information originate (1045)
summary-address This command aggregates routes learned from other protocols. Use the no
form to remove a summary address.
SYNTAX
[no] summary-address summary-address netmask
summary-address - Summary address covering a range of
addresses.
netmask - Network mask for the summary route.
COMMAND MODE
Router Configuration
DEFAULT SETTING
Disabled
COMMAND USAGE
Redistributing routes from other protocols into OSPF normally requires the
router to advertise each route individually in an external LSA. An
Autonomous System Boundary Router (ASBR) can be configured to
redistribute routes learned from other protocols by advertising an
aggregate route into all attached autonomous systems. This helps both to
decrease the number of external LSAs and the size of the OSPF link state
database.
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