[c-nsp] Rate-limiting ARPs

[Ed Butler]

I am trying to find out how to rate limit the generation of ARPs by a
gateway.

Example scenario:

==================================================
123.234.123.1/24 is a Cisco gateway connected to the Internet

An Internet host sends a UDP packet to 123.234.123.99

123.234.123.1 generates an ARP for the .99 IP address, but no one
answers it so it is down as "Incomplete"

An Internet host sends another UDP packet to 123.234.123.99

123.234.123.1 generates another ARP request
==================================================

>From what I can see, there is nothing that prevents this behaviour from
causing a DOS by flooding a subnet with ARP requests. What I'd like to
do is for the Cisco gateway (a 3750 in this instance) to remember it
sent an ARP request for the .99 IP address, and rate limit itself to
sending 1 every second or similar.

Is there any way of achieving this? Any fault with what I am suggesting?

Regards,

Ed Butler
RapidSwitch Ltd
DDI: 020 7106 0731

RapidSwitch Ltd, 5th Floor, Sovereign House, 227 Marsh Wall, London, E14
9SD

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