From: Eric Dumazet <eric.dumazet@gmail.com>
To: Tom Ammon <tom.ammon@utah.edu>
Cc: linux-kernel@vger.kernel.org, netdev <netdev@vger.kernel.org>
Subject: Re: how to tweak ARP timer on kernel 2.6.9
Date: Tue, 09 Mar 2010 23:10:14 +0100 [thread overview]
Message-ID: <1268172614.2872.122.camel@edumazet-laptop> (raw)
In-Reply-To: <4B96A24A.6060405@utah.edu>
Le mardi 09 mars 2010 à 12:32 -0700, Tom Ammon a écrit :
> Hi,
>
> I've been trying to figure out how to adjust the ARP timeout on kernel
> 2.6.9 and I found the following in /proc/sys/net/ipv4/neigh/ib0 (its an
> IB interface I am interested in changing) with the following values.
> This is on kernel 2.6.9-89ELsmp (RHEL4) :
>
> When I test this, along with per-flow ECMP (using the iproute2 utils), I
> see that the ARP cache is timing out about every 10 minutes (I observe
> this by load balancing an iperf flow between two different gateway
> machines and then graphing the interface traffic)
>
10 minutes seems out of specs.
> On a newer kernel, 2.6.18-164.11.1.el5 (RHEL5), I see mostly the same
> parms available, but a few new ones have been added. However, all of the
> parms that are the same name between the two kernels are the same values:
>
> Yet when I observe the same traffic flow with this machine, the ARP
> cache times out about once per minute.
>
This seems normal, old kernels were a bit lazy about arp.
> Is there another set of parameters somewhere that govern how often the
> kernel times out the ARP cache? If so, where might I find that? Is there
> any kernel documentation that talks about changing ARP timers on the
> linux kernel?
>
I would suggest :
man 7 arp
http://linux.die.net/man/7/arp
base_reachable_time
Once a neighbour has been found, the entry is considered to be
valid for at least a random value between base_reachable_time/2
and 3*base_reachable_time/2. An entry's validity will be
extended if it receives positive feedback from higher level
protocols. Defaults to 30 seconds.
gc_interval
How frequently the garbage collector for neighbour entries
should attempt to run. Defaults to 30 seconds.
gc_stale_time
Determines how often to check for stale neighbour entries. When
a neighbour entry is considered stale it is resolved again
before sending data to it. Defaults to 60 seconds.
and "ip -s neigh"
parent reply other threads:[~2010-03-09 22:10 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <4B96A24A.6060405@utah.edu>]
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