[cgl_discussion] new requirement about ARP cache updating on client machine based on Linux

Cress, Andrew R andrew.r.cress at intel.com
Tue Aug 12 06:02:30 PDT 2003

I agree, it would be more robust if the kernel sent a gratuitous ARP on
a change from ifconfig.  Having the middleware do this also works, but
timing is important here, so it is better if Linux does it.  I haven't
tried this on any 2.6 kernels yet, so I can't comment on whether this
has changed.


-----Original Message-----
From: Eric.Chacron at alcatel.fr [mailto:Eric.Chacron at alcatel.fr] 
Sent: Tuesday, August 12, 2003 8:51 AM
To: Peter Badovinatz
Cc: OSDL CGL Specs list; CGL Discussion
Subject: [cgl_discussion] new requirement about ARP cache updating on
client machine based on Linux

Hi Peter,

This is not a slam !

This is the third new requirement i propose on this list since 2.0 has
closed, and i hope having more feed back
from the lists than for the two first.
Note: The two first are: 1) scheduling priority configuration on Linux
internal threads
            2) RR quantum configuration.

This requirement is more cluster related and more precisely HA related.
I have the feed back that currently when one want to migrate an IP
from one machine to
another one on a local network using ifconfig, the ARP caches on the
clients remains with
the last value for a while, whereas ther's a need to switchover on the
address immediatly.
So , it seems that Linux doesn't send a gratuitous ARP upon ifconfig
some other OS ( Solaris, Tru64 ...).
Then HA implementations have to send this message "by hand".

I would like to get a confirmation of this behavior for the last Linux
releases, and ask for a change in Linux if every body agree.

Best regards,

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