SUMMARY: Arp table size limits

From: Charlie Dennett (dennett@Kodak.COM)
Date: Thu Apr 09 1992 - 16:02:48 CDT

Yes, Virginia, there is a limit to the size of the arp table.

Yesterday I asked if there was a limit to the size of the arp table.
It seems that the network people here told me one of my systems was
arping like crazy. The are 96 entries in the table but that is broken
down into 16 buckets of 6 entries each. From what I understand if a
bucket is full and an IP address you need to use is not in the table
but hashses to a full bucket, then it cannot continue and delays for
some amount of time before trying it all over again. A new arp request
is sent out after the delay. Voila, extra arp packets on the network.

There is a patch. The README me file is at the end of this summary.

Thanks to all who responded. The patch is going in over lunch today.

Charlie Dennett | Rochester Distributed Computer Services
Mail Stop 01816 | Customer Technical Support Services
Eastman Kodak Company | ---------------------------------------
Rochester, NY 14650-1816 | Internet: dennett@Kodak.COM


----- Begin Included Message -----

Patch-ID# 100361-03
Keywords: nfs, server, responding, due, arp, table, size
Synopsis: SunOS 4.1.1: server not responding due to limits of arp table
Date: 13/Feb/92
SunOS release: 4.1.1

Unbundled Product:
Unbundled Release:
Topic: Arp table size
BugId's fixed with this patch: 1043580

Architectures for which this patch is available: sun4 sun4c sun3

Patches which may conflict with this patch:

Obsoleted by:

Update -03, 21-Jan-92
Increased the arp table size from 512 to 1024.
compiled a new arp

Update -02, 28-Aug-91
Added patchid string to if_ether.c

Problem Description:
NFS clients experience "server no responding" errors which effect
nfs and uptime. This idle state can last for a minute to hours.
The arp request is repeatedly sent over and over again until finally
able to update arp table with client's address. Once client's address
is in arp table systems work fine.

One more thing noticed is that entries were deleted last-in last first-out
versus first-in first-out like stated in the source code.


Backup system before doing this!

mv /sys/`arch -k`/OBJ/if_ether.o /sys/`arch -k`/OBJ/if_ether.o.FCS

cp if_ether.o /sys/`arch -k`/OBJ/

         Please Refer to the System and Networking Administration Manual
             section on building and installing a custom kernel.

Rebuild and install the new kernel.

mv /usr/etc/arp /usr/etc/arp.FCS
cp arp /usr/etc

use chmod and chown to set premissions of arp as follows:
-rwxr-sr-x 1 root kmem 16384 Oct 2 15:45 /usr/etc/arp*


----- End Included Message -----

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:06:40 CDT