IP Routing ISIS
Chapter: Integrated IS-IS Commands: A through I
Chapter Contents
advertise-passive-only
To configure Intermediate System-to-Intermediate System (IS-IS) to advertise only prefixes that belong to passive interfaces, use the advertise-passive-only command in router configuration mode. To remove the restriction, use the no form of this command.
advertise-passive-only
no advertise-passive-only
Syntax Description
This command has no arguments or keywords.
Defaults
This command has no default behavior.
Command Modes
Router configuration
Command History
ReleaseModification
12.0(22)S
This command was introduced.
12.3(2)T
This command was integrated into Cisco IOS Release 12.3(2)T.
12.2(27)SBC
This command was integrated into Cisco IOS Release 12.2(27)SBC.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX
This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
Usage Guidelines
This command is an IS-IS mechanism to exclude IP prefixes of connected networks from link-state packet (LSP) advertisements, thereby reducing IS-IS convergence time.
Configuring this command per IS-IS instance is a scalable solution to reduce IS-IS convergence time because fewer prefixes will be advertised in the router nonpseudonode LSP.
This command relies on the fact that when enabling IS-IS on a loopback interface, you usually configure the loopback as passive (to prevent sending unnecessary hello packets out through it because there is no chance of finding a neighbor behind it). Thus, if you want to advertise only the loopback and if it has already been configured as passive, configuring the advertise-passive-only command per IS-IS instance would prevent the overpopulation of the routing tables.
An alternative to this command is the no isis advertise-prefix command. The no isis advertise-prefix command is a small-scale solution because it is configured per interface.
Examples
The following example uses the advertise-passive-only command, which affects the IS-IS instance, and thereby prevents advertising the IP network of Ethernet interface 0. Only the IP address of loopback interface 0 is advertised.
!interface loopback 0ip address 192.168.10.1 255.255.255.255no ip directed-broadcast!!interface Ethernet0ip address 192.168.20.1 255.255.255.0no ip directed-broadcastip router isis!.!.!.!router isispassive-interface Loopback0net 47.0004.004d.0001.0001.0c11.1111.00advertise-passive-onlylog-adjacency-changes!