Date: Sun, 31 Dec 2000 05:49:11 -0500 From: "Louis A. Mamakos" <louie@TransSys.COM> To: Gerhard Sittig <Gerhard.Sittig@gmx.net> Cc: freebsd-current@FreeBSD.ORG Subject: Re: IGMP queries Message-ID: <200012311049.eBVAnBr23486@whizzo.transsys.com> In-Reply-To: Your message of "Sat, 30 Dec 2000 21:52:41 %2B0100." <20001230215241.M253@speedy.gsinet> References: <001f01c07286$9a055a00$0e00a8c0@neland.dk> <20001230215241.M253@speedy.gsinet>
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> > > Btw, can I use IGMP to something useful/interesting/funny? > > AFAIK it's some kind of dynamic route establishment (learning > about topology by listening to what your neighbour knows about > the network). Home users and small LANs won't need it IMHO, > maybe WAN links will benefit? But I'm definitely not keen on > having "the world" tell me where to send my packets to. I just > hand the traffic to my provider's dialin port. :> IGMP is the protocol used between a multicast router, and end-hosts on a subnetwork; much like ICMP is used between a router and an end-host to help manage unicast traffic. So, when your hosts joins a multicast group, it sends (to a multicast group) an IGMP message announcing this. This is supposed to cause a multicast router on the subnetwork to begin forwarding the traffic onto the subnet. The multicast router will also periodically send IGMP group membership queries onto the subnetwork to see if there are any hosts still interested/subscribed to a group. If it gets no replies after a while, it will stop forwarding unsubscribed groups onto that subnetwork. So that's why you're seeing IGMP queries; the multicast router is trying to see if you've joined any multicast groups so it can try to send you traffic. It's got nothing to do with "having the world tell you where to send your packets to." louie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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