Date: Fri, 19 Aug 2005 22:30:35 -0700 From: Julian Elischer <julian@elischer.org> To: Paul Khavkine <paul@distributel.net> Cc: freebsd-net@freebsd.org Subject: Re: Reading raw ethernet Message-ID: <4306BFFB.8060307@elischer.org> In-Reply-To: <20050819182437.R47954-100000@krusty.mtl.distributel.net> References: <20050819182437.R47954-100000@krusty.mtl.distributel.net>
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Paul Khavkine wrote: > On Fri, 19 Aug 2005, Julian Elischer wrote: > > >>Paul Khavkine wrote: >> >>>Hi guys. >>> >>> >>>I'm writing a small program to read raw ethernet frames out of netgraph >>>to capture Spannign Tree packets from the switch. >>> >>>Is it possible to pick up STP frames without putting the interface in >>>promiscuous mode ? >> >>If you don't put it in promiscuous mode, then you will only see broadcast >>packets and packets aimed at you specifically. >> >>If that's enough then there is nothing in netgraph that insists that >>you turn on promiscuous mode. > > > Well STP packets are sent to a well known MAC address (multicast?) > so i can't see it if the card is not in promisc mode. Well it might be a multicast address. I'm not an expert on multicast.. I've never really used it. I think that it depends on what hardware you have as to how it deals with M/C. > I'm not exactly sure if it's good or not to leave it in promisc mode > all the time, is there any security/performance issues with that on a > busy server? some.. usually though the switch is only going to send you packets you might want to receive anyhow.. > I want to read STP packets to monitor the link with the switch, if i can't > hear the switch for X amount oof time, failover to another NIC. > Is it possible to have more then one MAC on a NIC ? I have bge and em > cards. I've never heard of it.. > > >>You should probably look at the ng_etf node too BTW. > > > How does ng_etf deal with that ? no, but as an example of something that is designed to be attached directly to the ng_ether nodes. >
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