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set-overload-bit
Configures the router to advertise itself as overloaded.
Syntax: [no] set-overload-bit [on-startup seconds] [suppress external | interlevel | external interlevel]
on-startup seconds
Set the overload bit during system startup or restart for the specified number of seconds. Valid values are 5 - 86400.
Description: When enabled, the overload bit instructs other routers not to use this router as an intermediate hop in their SPF computations. No paths through this router are visible to other routers in the area. IP and CLNS prefixes directly connected to this router are reachable.
The following are circumstances where it may be advantageous to enable the overload bit:
- During startup this router may be too busy with the tasks associated with convergence to forward traffic. Use the on-startup keyword to configure the router to temporarily set the overload bit during convergence.
- The router is in a test network that has connections to a production network. The overload bit prevents traffic from moving between the two networks.
When routers detect that overload bit is set for a particular system, the router with the overload bit set will not be used for transit traffic. The router with the overload bit set will be used for packets destined to the overloaded router's directly connected networks and IP prefixes. Directly connected interfaces/IP prefixes, redistributed routes and leaked routes are reachable on Avici routers with the overload bit set.
ISPs may want to suppress certain IP prefixes from being advertised in the router's own LSPs when set-overload-bit is configured. For example, it may not be desirable to allow Level 1 into Level 2 IP prefix propagation, which would make the router a transit node for IP traffic. This enhancement allows an IS-IS Level 1 - Level 2 (L1L2) router which is redistributing IP routes from Level 1 into Level 2 or Level 2 into Level 1 to stop advertising these redistributed routes in its LSP when the overload bit has been set.
Use the set-overload-bit on-startup seconds command to configure the router to temporarily set the overload bit during startup.
Use the set-overload-bit suppress external keyword, to suppress advertisement of IP prefixes learned from other protocols when the overload bit is set.
Use the set-overload-bit suppress interlevel keyword, to suppress advertisement of IP prefixes learned from other IS-IS levels when overload bit is set.
Use the set-overload-bit suppress external interlevel keyword, to suppress the advertisement of IP prefixes learned from both other protocols and IS-IS levels when the overload bit is set.
Use the set-overload-bit command to enable the overload bit.
Use the no set-overload-bit command to disable the overload bit.
Factory Default: No overload bit configured.
Command Mode: Router configuration.
Example: In the following example:
- The router isis command enables IS-IS on the router, specifies an IS-IS instance, and changes the command mode to Router configuration,
- The set-overload-bit on-startup 60 command configures the router to enable the overload bit for 60 seconds at router startup.
- The suppress interlevel keyword configures the router to suppress advertisement of IP prefixes learned from other IS-IS levels during the 60 seconds that the overload bit is set:
router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
router(config)#router isis tsr
router(config-router)#set-overload-bit on-startup 60 suppress interlevel
router(config-router)#end
router#
Related Commands: router isis
show isis database
show running-config
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Copyright © 2004
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: ISIS42.html
Last Updated: 05/10/04 at 16:35:45