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How to map an IP address to a Multicast MAC Adress

This BSCI Guide shows three Multicast IP addresses that map to the same Multicast MAC address but I think only two of them do.

IP would not map to 0100.5e40.0305 it would map to 0100.5e31.0305?

Is this a mistake/typo from Cisco? Or am I missing something?

I also think the sentence "Notice that the first two octets can vary in the IP addresses" is not quite accurate.

Shouldn't it say "Notice that the first octet and the first bit of the second octet can vary in the IP addresses"?

 CCNP BSCI Quick Reference Sheets
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"I also think the  sentence "Notice that the first two octets can  vary in the IP addresses"  is not quite accurate.

Shouldn't it  say "Notice that the first  octet and the first bit of the second octet  can vary in the IP  addresses"?"
 Well you are correct but if the first bit changes that means the whole  second octet can be different even though that is the only bit changing. But yeah a more specific description would be better.
as for the examples i agree the that address would map to 0100.5e31.0305. For the mac addresses to overlap the first 4 must be 1110 (to be multicast) and the last 23 must be the same but those 5 in between can be whatever. This will create your overlapping MACs.

Hope this helps

That is one thing i always like about cisco press cert guides, there are always enough errors to keep you on your feet and think through everything they are telling you.


thanks that1guy15,

I just wanted to make sure that I was not missing something!

The mistakes that I catch quickly don't bother me as much as the ones that make me think that I don't understand something or the ones that I never catch.
Well the ones that make you think also force you to dig into the subject deeper than you normally would. Once you figure it out you are in the end stronger on the subject.