Command:

ip ospf demand-circuit


Mode:

Router(config-if)#


Syntax:

ip ospf demand-circuit
no ip ospf demand-circuit

 

Syntax Description:

This command has no arguments or keywords.

 

Command Description:

To configure OSPF to treat the interface as an OSPF demand circuit, use the ip ospf demand-circuit command in interface configuration mode. To remove the demand circuit designation from the interface, use the no form of this command.

On point-to-point interfaces, only one end of the demand circuit must be configured with this command. Periodic hello messages are suppressed and periodic refreshes of link-state advertisements (LSAs) do not flood the demand circuit. This command allows the underlying data link layer to be closed when the topology is stable. In point-to-multipoint topology, only the multipoint end must configured with this command.

The circuit is not a demand circuit by default.


Example:

The following example configures the BRI 0/0 interface as a demand-circuit:

Router(config)#interface bri 0/0
Router(config-if)#ip ospf demand-circuit


Misconceptions:

A common misconception is that this command is the only command necessary to efficiently run OSPF over an ISDN line. Care should also be taken to ensure that OSPF topology rules are followed when an ISDN line is up. The router should also be configured and monitored to ensure that the OSPF cost of an ISDN interface does not change due to PPP multilink. Without proper configuration, it is possible for a router to continuously dial an ISDN interface in order to send unnecessary LSAs.


Related Commands:

ip ospf hello-interval

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