Cisco Systems 78-11741-02 Configuring Nhrp Authentication, Controlling the Triggering of Nhrp

Configuring IP Addressing

Configuring Address Resolution Methods

Configuring NHRP Authentication

Configuring an authentication string ensures that only routers configured with the same string can communicate using NHRP. Therefore, if the authentication scheme is to be used, the same string must be configured in all devices configured for NHRP on a fabric. To specify the authentication string for NHRP on an interface, use the following command in interface configuration mode:

Command	Purpose
Router(config-if)#ip nhrp authentication string	Specifies an authentication string.

Controlling the Triggering of NHRP

On any platform, there are two ways to control when NHRP is triggered. These methods are described in the following sections:

•Triggering NHRP by IP Packets

•Triggering NHRP on a per-Destination Basis

Triggering NHRP by IP Packets

You can specify an IP access list that is used to decide which IP packets can trigger the sending of NHRP requests. By default, all non-NHRP packets trigger NHRP requests. To limit which IP packets trigger NHRP requests, define an access list and then apply it to the interface.

To define an access list, use the following commands in global configuration mode as needed:

Command	Purpose
Router(config)# access-listaccess-list-number {deny permit} source	Defines a standard IP access list.
[source-wildcard]
Router(config)# access-list access-list-number{deny permit}	Defines an extended IP access list.
protocol source source-wildcard destination destination-wildcard
[precedence precedence] [tos tos] [established] [log]

To apply the IP access list to the interface, use the following command in interface configuration mode:

Command	Purpose
Router(config-if)# ip nhrp interest access-list-number	Specifies an IP access list that controls
	NHRP requests.

Cisco IOS IP Configuration Guide

IPC-22