arp-detect

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 12.3X48-D65 and Junos OS Release 15.1X49-D130.

Description

Define the length of time (in milliseconds) for an SPU to wait for an acknowledgement from the Routing Engine that an ARP request has been received from the SPU. If the Routing Engine fails to respond within the specific time interval, the SPU considers that the Routing Engine CPU utilization is high at that moment, and initiates the ARP throttling. ARP throttling is initiated on the logical interface, where the incoming packet had triggered the ARP request.

Configuring a shorter ARP detect time interval results in triggering of ARP throttling more frequently. Frequent ARP throttling is useful for lowering Routing Engine CPU utilization caused by excessive ARP requests.

For example, when you configure the set forwarding-options nexthop arp-detect 300 option, the nexthop resolution request must be acknowledged by the Routing Engine within 300 milliseconds. If the SPU does not get an acknowledgment from the Routing Engine in 300 milliseconds, the logical interface which had received the packet that triggered the nexthop request, changes into ARP throttle state. While the ARP throttle state is active for that interface, traffic entering into that interface does not trigger new nexthop resolution requests.

Caution

We recommend that only advanced Junos OS users attempt to configure ARP throttle and ARP detect feature. Because, improper configuration might result in high CPU utilization of Routing Engine affecting other processes on your device.

Options

milliseconds—Number of seconds the SPU waits before receiving a response from Routing Engine.

Range: 1 through 10000 milliseconds

Default: 10000 milliseconds

Required Privilege Level

security—To view this statement in the configuration.

security-control—To add this statement to the configuration.

Related Documentation