Date: Wed, 14 Mar 2012 16:15:48 -0700 From: Chuck Swiger <cswiger@mac.com> To: Adarsh Joshi <adarsh.joshi@qlogic.com> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Zero MAC address Message-ID: <B6C73A35-BEC9-425F-B9F0-B1C091B5BE97@mac.com> In-Reply-To: <5E4F49720D0BAD499EE1F01232234BA87438162FAE@AVEXMB1.qlogic.org> References: <5E4F49720D0BAD499EE1F01232234BA87438162F95@AVEXMB1.qlogic.org> <1AB6F524-B4F4-4718-96C5-DB2951A02D59@mac.com> <5E4F49720D0BAD499EE1F01232234BA87438162FAE@AVEXMB1.qlogic.org>
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On Mar 14, 2012, at 4:05 PM, Adarsh Joshi wrote: > Thank you for the quick replies. > > I am aware of the importance of the second bit. By invalid, I was wondering if that particular address is reserved or if it has any special meaning or purpose. There isn't a special meaning for all-zeros MAC to my knowledge, although all-ones MAC is subnet-local broadcast. > So in theory, I cannot classify it as an invalid MAC address on my packet statistics utility. Yes, as far as theory goes. In practice, all-zeros MACs tend to indicate that an ethernet driver failed to read the burned-in MAC assigned to the NIC. :-) > On a side thought, can an incoming packet be classified as "invalid MAC address" if it has the same MAC address of the host? Tentatively, yes-- MACs are supposed to be unique, and any collision is bad...just be careful that you aren't seeing packets which your local host had sent (perhaps because of a L2 switching loop). Regards, -- -Chuck
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