Date: Mon, 7 Nov 2005 10:19:27 -0500 From: Bill Vermillion <bv@wjv.com> To: Gleb Smirnoff <glebius@freebsd.org> Cc: arch@freebsd.org Subject: Re: ARP request retransmitting Message-ID: <20051107151927.GD1830@wjv.com> In-Reply-To: <20051107140451.GU91530@cell.sick.ru> References: <20051107140451.GU91530@cell.sick.ru>
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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
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