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Configuring IP Addressing
Configuring Address Resolution Methods
IPC-23
Cisco IOS IP Configuration Guide
Triggering NHRP on a per-Destination Basis
By default, when the software attempts to send a data packet to a destination for which it has determined
that NHRP can be used, it sends an NHRP request for that destination. To configure the system to wait
until a specified number of data packets have been sent to a particular destination before NHRP is
attempted, use the following command in interface configuration mode:
Triggering NHRP Based on Traffic Thresholds
NHRP can run on Cisco Express Forwarding (CEF) platforms when NHRP runs with BGP over ATM
media. You can configure NHRP to initiate switched virtual circuits (SVCs) once a configured traffic
rate is reached. Similarly, SVCs can be torn down when traffic falls to another configured rate.
Prior to Cisco IOS Release 12.0, a single packet could trigger an SVC. Now you can configure the traffic
rate that must be reached before NHRP sets up or tears down an SVC. Because SVCs are created only
for burst traffic, you can conserve resources.
Restrictions
Cisco IOS releases prior to Release 12.0 implemented NHRP draft version 4. Cisco IOS Release 12.0
and later implements NHRP draft version 11. These versions are not compatible. Therefore, all routers
running NHRP in a network must run the same version of NHRP in order to communicate with each
other. All routers must run Cisco IOS Release 12.0 and later, or all routers must run a release prior to
Release 12.0, but not a combination of the two.
Additional restrictions:
• They work on CEF platforms only.
• They work on ATM media only.
• BGP must be configured in the network where these enhancements are running.
Prerequisites
Before you configure the feature whereby NHRP initiation is based on traffic rate, the following
conditions must exist in the router:
• ATM must be configured.
• CEF switching or distributed CEF (dCEF) switching must be enabled.
• BGP must be configured on all routers in the network.
If you have CEF switching or dCEF switching and you want NHRP to work (whether with default values
or changed values), the ip cef accounting non-recursive command must be configured.
Command Purpose
Router(config-if)# ip nhrp use usage-count
Specifies how many data packets are sent to a destination before NHRP
is attempted.