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484 C
HAPTER
19: O
PEN
S
HORTEST
P
ATH
F
IRST
(OSPF) R
OUTING
Router IDs
Each router that is configured for OSPF has an OSPF router ID. The OSPF
router ID uniquely identifies the router to other routers within an
autonomous system.
The router ID determines the designated router in a broadcast network if
the priority values of the routers involved in the designated router
election are equal. In the event of a
priority tie, the router with the
highest router ID is elected designated router for the area.
Three types of router identifiers, in the form of an IP address, are
available:
■
Default — A unique ID that the system generates and uses as the
default router ID.
■
Interface — The index of an IP interface on the router.
■
Address — An ID that you define in the form of an IP address.
OSPF routing must be inactive before you can add or modify an OSPF
router ID. To deactivate OSPF routing, set the OSPF mode to
disabled
.
See the Command Reference Guide for details. After you add the router
ID, you can set the OSPF mode to
enabled
on the interface.
Important
Considerations
Consider the following guidelines when you configure OSPF router IDs:
■
For OSPF to operate correctly, the router ID must be unique for every
router.
■
Choose the default setting to ensure unique router IDs.
■
You cannot set the router ID to either 0.0.0.0 or 255.255.255.255.