Date: Fri, 11 Nov 2005 14:09:26 +0000 From: Bruce M Simpson <bms@spc.org> To: Gleb Smirnoff <glebius@FreeBSD.org> Cc: arch@FreeBSD.org Subject: Re: ARP request retransmitting Message-ID: <20051111140926.GC733@empiric.icir.org> In-Reply-To: <20051107140451.GU91530@cell.sick.ru> References: <20051107140451.GU91530@cell.sick.ru>
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On Mon, Nov 07, 2005 at 05:04:51PM +0300, Gleb Smirnoff wrote: > 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? In response to the other replies to this thread citing broadcast pollution on Ethernet-based networks: Please add this functionality under a sysctl where it is turned off by default. It is desirable in situations where ARP entries cached further upstream are stale, but it may cause flooding in an environment where the layer 2 backbone hasn't been split or has not been segregated well. Other people cited examples where vendor switch implementations were retransmitting across VLANs -- this week I've been offering moral support to a friend who is dealing with similar VLAN brokenness at his $DAYJOB (there was an extension to 802.1d to support multiple spanning tree instances across VLANs which I think not everyone supports correctly). Regards, BMS
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