[Eug-lug] arp kernel voodoo question for the gurus.

[Mike Cherba]

Larry,
	I did a little digging and I finally found something that appears to
confirm my idea that gc_stale_time is the answer.
http://linux-ip.net/html/ether-arp.html
you will  want to change this for the interface in question, as the
default values only get used when creating new interfaces.

			-Mike

Computers are useless. They can only give you answers. -- Pablo Picasso

On Fri, 2007-08-17 at 16:19 -0700, larry price wrote:
> I have a need to shorten the time between arp requests for a specific
> machine running a 2.6 kernel.
> 
> looking at the various sysctls available (sysctl entries map to /proc/sys/)
> I see the following groups of variables that may be germane
> 
> net.ipv4.conf.eth0.arp_accept = 0
> net.ipv4.conf.eth0.arp_ignore = 0
> net.ipv4.conf.eth0.arp_announce = 0
> net.ipv4.conf.eth0.arp_filter = 0
> net.ipv4.neigh.default.app_solicit = 0
> net.ipv4.conf.default.proxy_arp = 0
> 
> and the following time specifications that may be relevant.
> 
> net.ipv4.neigh.default.base_reachable_time_ms = 30000
> net.ipv4.neigh.default.retrans_time_ms = 1000
> net.ipv4.neigh.default.gc_thresh3 = 1024
> net.ipv4.neigh.default.gc_thresh2 = 512
> net.ipv4.neigh.default.gc_thresh1 = 128
> net.ipv4.neigh.default.gc_interval = 30
> 
> But aside from man (7) arp
> and /usr/src/linux/ip-sysctl.txt
> 
> I am not finding good documentation that tells me what I need to know.
> 
> So if anyone here has any idea about how the various knobs available
> to tune arp caching actually interact I (and google) would be much
> obliged if you could enlighten me.
> 
> Now I could work around the problem by using arping from cron, but
> that is hacky and error prone and I would really rather have a clean
> solution.
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