Cisco Systems 78-11741-02 Configuring IS-IS Authentication Passwords, Summarizing Address Ranges

Configuring Integrated IS-IS

Miscellaneous IS-IS Parameters Configuration Task List

Configuring IS-IS Authentication Passwords

You can assign passwords to areas and domains.

The area authentication password is inserted in Level 1 (station router level) LSPs, and the routing domain authentication password is inserted in Level 2 (area router level) LSPs.

To configure either area or domain authentication passwords, use the following commands in router configuration mode, as needed:

Command	Purpose
Router(config-router)# area-passwordpassword	Configures the area authentication password.
Router(config-router)# domain-passwordpassword	Configures the routing domain authentication password.

Summarizing Address Ranges

You can create aggregate addresses that are represented in the routing table by a summary address. This process is called route summarization. One summary address can include multiple groups of addresses for a given level. Routes learned from other routing protocols also can be summarized. The metric used to advertise the summary is the smallest metric of all the more-specific routes.

To create a summary of addresses for a given level, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# summary-address	Creates a summary of addresses for a given level.
address mask {level-1 level-1-2 level-2}

Setting the Overload Bit

You can configure the router to set the overload bit (also known as the hippity bit) in its nonpseudonode LSPs. Normally the setting of the overload bit is allowed only when a router runs into problems. For example, when a router is experiencing a memory shortage, the link-state database may not be complete, resulting in an incomplete or inaccurate routing table. By setting the overload bit in their LSPs, other routers can ignore the unreliable router in their shortest path first (SPF) calculations until the router has recovered from its problems.

The result will be that no paths through this router are seen by other routers in the IS-IS area. However, IP and CLNS prefixes directly connected to this router will be still be reachable.

This command can be useful when you want to connect a router to an IS-IS network, but do not want real traffic flowing through it under any circumstances. Examples are as follows:

•A test router in the lab, connected to a production network.

•A router configured as an LSP flooding server, for example, on an NBMA network, in combination with the mesh-group feature.

•A router that is aggregating virtual circuits (VCs) used only for network management. In this case, the network management stations must be on a network directly connected to the router with the set-overload-bitrouter configuration command configured.

Cisco IOS IP Configuration Guide

IPC-285