Date: Mon, 7 Nov 2005 18:17:51 -0500 From: Charles Swiger <cswiger@mac.com> To: John-Mark Gurney <gurney_j@resnet.uoregon.edu> Cc: arch@freebsd.org, Garance A Drosihn <drosih@rpi.edu> Subject: Re: ARP request retransmitting Message-ID: <CE57F103-4C41-492E-9A5C-789B67A7D158@mac.com> In-Reply-To: <20051107224338.GE775@funkthat.com> References: <20051107140451.GU91530@cell.sick.ru> <436F7DDB.40703@mac.com> <p06230904bf9542d696b6@[128.113.24.47]> <20051107224338.GE775@funkthat.com>
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On Nov 7, 2005, at 5:43 PM, John-Mark Gurney wrote: >> While that "other hand" is true, here at RPI we deal with some of >> those other-hand issues by simply turning them off. We turn off >> multi-cast by default on some of our networks, for instance. But >> there's no way we can turn off ARP, so I think more care needs to >> be taken to make sure ARP remains network-friendly. > > And most places that have VERY large number of hosts in a broadcast > domain (a partially populated class b), have smart switches that cache > arp requests, and prevent the arp traffic from killing the network... Really? You're saying that "tcpdump -nt arp" never shows any requests except those made by the local host? Which vendor and which switch model? Smart switches will generally keep track of 1000 or 4000 or so MAC addresses and the ports those MACs are associated with, but I am not aware of anything in them which blocks ARP traffic or anything else which uses the all-ones broadcast MAC address. I can see ARP requests going out from any/all of the other machines on the network I'm using right now (using several 3com SuperStack 3300's), and I've seen the same thing on networks using the HP Procurve or Cisco 29xx switches. -- -Chuck
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