ARP request retransmitting

[Bill Vermillion]

On Mon, Nov 07, 2005 at 17:04 , the primordial soup was bombarded
 with cosmic radiation and a new life form of genus Gleb Smirnoff
emerged to test its air breathing capabilities and with great
effort gasped:

>   Colleagues,

>   I have a proposition on changing the behavior of ARP retransmitting.
> Currently we after sending several ARP requests, sending ARP requests
> for given IP is suppressed for some interval (by default 20 seconds).
> Probably this feature was designed in early 90th, when sending one
> additional broadcast packet was an expensive thing.

The man page says the host is considered down "for a short period
(normally 20 seconds), allowing an error to be returned to
transmission attempts in this interval".

>   I suggest to keep sending ARP requests while there is a demand for
> this (we are trying to transmit packets to this particular IP),
> ratelimiting these requests to one per second. This will help in a
> quite common case, when some host on net is rebooting, and we are
> waiting for him to come up, and notice this only after 1 - 20 seconds
> since the time it is reachable.

>   Any objections?

Is the 20 second limit that much of a problem.  And the 20 minute
timeout for caching is certainly far more generous that my old
big Cisco that had a 4 hour cache.  A user complained that he put
up new machines and things weren't working.  I told him he should
have called me before he put the IPs back the way they were as
cleanring the arp-cache took care of that.

How big is your network?

Bill
-- 
Bill Vermillion - bv @ wjv . com