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default-information originate
Enables IS-IS default route origination on this router.
[no] default-information originate [route-map map-tag]
map-tag
Specifies the route-map name containing the criteria that must be satisfied for the default route to be generated. Default Value: No route-map specified.
Description: IS-IS default route origination provides for the generation of a default route when the router is either a Level-2 or Level-1-2 router. Default route origination has no affect on IS-IS Level-1 routers. The Level-1 router determines the default route by examining the nearest Level-1-2 router with the ATT bit set in its Level-1 LSP. If the IS-IS type is changed from Level-1 to Level-2 or Level-1-2, the router will originate the default route based on the route-map. If a router is configured for default route origination, IS-IS will originate an advertisement 0.0.0.0 in its Level-2 link state packets.
A route-map can be used to advertise 0/0 conditionally. With a match IP address standard access-list command, specify one or more IP routes that must exist for the router to advertise 0/0.
If a route-map is specified and one or more routes in the routing table qualifies any of the access-list or prefix-list conditions, the default route is originated. If the router receives an LSP with the default route, it will install the default route unconditionally. In the event of a default route being redistributed from other routing protocols, default route origination will take the precedence and replace the export entry.
Enabling IS-IS default route origination is recommended for scenarios such as the following:
- The router is an ASBR router and running BGP with external peers.
- As a result of network policy this border router is chosen for default traffic.
- The router is connected to an ASBR not running IS-IS.
Use the default-information originate command to enable default route origination on this router.
Use the no default-information originate command to disable default route origination on this router. Specifying any Option with the no command only changes the option to its default value leaving the remainder of the configuration unchanged.
Factory Default: Disabled
Command Mode: Router IS-IS.
Example 1: The following example forces the generation of a default route into the IS-IS domain if the route-map criteria are met:
router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#router isis 1
router(config-router)#net 35.0001.0000.0011.1010.00
router(config-router)#is-type level-2
router(config-router)#default-information originate route-map r1
router(config-router)#show
!
router isis 1
net 35.0001.0000.0011.1010.00
is-type level-2-only
default-information originate route-map r1
!
router#
Example 2: The following example removes the route map configured in example 1 from the default route origination configuration:
router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#router isis 1
router(config-router)#net 35.0001.0000.0011.1010.00
router(config-router)#is-type level-2
router(config-router)#default-information originate
router(config-router)#show
!
router isis 1
net 35.0001.0000.0011.1010.00
is-type level-2-only
default-information originate
!
router#
Example 3: The following example removes the default route origination configuration for this router:
router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#router isis 1
router(config-router)#no default-information originate
!
router isis 1
net 35.0001.0000.0011.1010.00
is-type level-2-only
!
router#
Related Commands: router isis
show
show isis
show running-config isis
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Copyright © 2005
Avici Systems Inc.
Avici® and TSR®
is a registered trademark of Avici Systems Inc.
IPriori™, Composite Links™, SSR™, QSR, and NSR® are
trademarks of Avici Systems Inc.
Source
File Name: ISIS.fm
HTML File Name: ISIS5.html
Last Updated: 02/25/05 at 14:55:50