Configuring Integrated IS-IS
Miscellaneous IS-IS Parameters Configuration Task List
IPC-286
Cisco IOS IP Configuration Guide
Unless you specify the on-startup keyword, this command sets the overload bit immediately and it
remains set until the no set-overload-bit command is specified. If you specify the on-startup keyword,
you must indicate whether it is set for a specified number of seconds or until BGP has converged. If BGP
does not signal IS-IS that it has converged, IS-IS will turn off the overload bit after 10 minutes.
In addition to setting the overload bit, you might also want to suppress certain types of IP prefix
advertisements from LSPs. For example, allowing IP prefix propagation between Level1 and Level 2
effectively makes a node a transit node for IP traffic, which may be undesirable. The suppress keyword
used with the interlevel or external keyword (or both) accomplishes that suppression while the overload
bit is set.
To set the overload bit, use the following command in router configuration mode:
Changing the Routing Level for an Area
You can change the routing level configured for an area using the is-type router configuration command.
If the router instance has been configured for a Level1-2 area (the default for the first instance of the
IS-IS routing process in a Cisco router), you can remove Level2 (interarea) routing for the area using
the is-type command and change the routing level to Level1 (intra-area). You can also configure Level2
routing for an area using the is-type command, but the instance of the IS-IS router configured for Level2
on the Cisco router must be the only instance configured for Level2.
To change the routing level for an IS-IS routing process in a given area, use the following command in
router configuration mode:
Tuning LSP Interval and Lifetime
By default, the router sends a periodic LSP refresh every 15 minutes. LSPs remain in a database for
20 minutes by default. If they are not refreshed by that time, they are deleted. You can change the LSP
refresh interval or the LSP lifetime. The LSP interval should be less than the LSP lifetime or else LSPs
will time out before they are refreshed. The software will adjust the LSP refresh interval if necessary to
prevent the LSPs from timing out.
Command Purpose
Router(config-router)# set-overload-bit
[on-startup {seconds | wait-for-bgp}]
[suppress {[interlevel] [external]}]
Sets the overload bit.
Command Purpose
Router (config)# is-type {level-1 | level-1-2 |
level-2-only}
Configures the routing level for an instance of the IS-IS routing
process.