Just binary math my friend :-)

The last 3 octets are all 1, so match everything.

First octet:
11100000 = 224
00000111 = 7

Meaning that everything matches from 11100000 up to 11100111

11100111 = 231

Class D addresses reach from 224 to 239, so Class D is 16 subnets large. Half 
of 16 is 8 when matching 224 up to 231 you have your 8 subnets which is half of 
the multicast range :-)




-- 
Regards,

Rick Mur
CCIE2 #21946 (R&S / Service Provider)
Sr. Support Engineer – IPexpert, Inc.
URL: http://www.IPexpert.com

On 26 dec 2009, at 15:55, Ahmed Haji Munye wrote:

> 
> Hi
> 
> On the detailed solution task 24.3, it says " Set R2 to advertise itself as 
> as the RP for the first half of all groups"
> 
> My question is from where did you get the multicast 224.0.0.0 7.255.255.255 ?
> 
> Regards
> Ahmed
> 
> Ta semester! - sök efter resor hos Kelkoo. 
> Jämför pris på flygbiljetter och hotellrum: 
> http://www.kelkoo.se/c-169901-resor-biljetter.html
> _______________________________________________
> For more information regarding industry leading CCIE Lab training, please 
> visit www.ipexpert.com

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