VSP 7000: IP ARP Limit

Doc ID		SOLN273276
Version:		1.0
Status:		Published
Published date:		11 Aug 2015

Author:

fbarone

Details

What is the IP ARP Limit on the VSP 7000 running version 10.3.3.0 and what happens when the limit is reached.

Problem Clarification

What is the IP ARP capacity of the VSP 7000 and what happens when we reach that limit. Also, what can be done to try to help get around that limit.

Cause

On VSP7000 the number of dynamically learned ARP entries is limited to 4096 entries.

When the system detects traffic for an unknown IP address, the first packet in that traffic stream is captured to the CPU and the software agent will send an ARP request.

If, and when the ARP reply is received, we add a new ARP entry associated with the destination IP address, only if the number of already dynamically learned ARP entries is below 4096. Otherwise it will refuse to add it and if there is a continuous request for traffic to reach that IP address it will try to resolve and add the ARP address again in about 20 seconds.

Solution

ARP aging is based on the ARP timeout configured value ((config)#arp timeout X), and on the MAC address aging time.

Check the setting for ARP timeout. The default is 360 minutes. If this is set to the default, then try to lower the ARP aging time to 60 minutes.

Along with a maximum of 4096 dynamic ARP entries we support up to 256 static ARP entries.

This will allow for up to 256 other dynamic ARP entries to be learned.

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