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Configuring IP Addressing
Configuring Address Resolution Methods
IPC-22
Cisco IOS IP Configuration Guide
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:
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:
To apply the IP access list to the interface, use the following command in interface configuration mode:
Command Purpose
Router(config-if)# ip nhrp authentication string
Specifies an authentication string.
Command Purpose
Router(config)# access-list access-list-number {deny | permit} source
[source-wildcard]
Defines a standard IP access list.
Router(config)# access-list access-list-number {deny | permit}
protocol source source-wildcard destination destination-wildcard
[precedence precedence] [tos tos] [established] [log]
Defines an extended IP access list.
Command Purpose
Router(config-if)# ip nhrp interest access-list-number
Specifies an IP access list that controls
NHRP requests.