IE lab 5 question 5.2 Mulicast RP and mapping agent

From: Dane Newman (dnewman@datasc.com)
Date: Wed Dec 05 2007 - 06:23:41 ART


Hello Experts

I have a question. In task 5.2 it asks us to have R5 be the RP for
multicast groups 226.0.0.0 - 238.255.255.255 and R1 to map those multicast
groups to R5. It also states to use the minimum number of access lists and
access list entries to do this task.

In the solutions guide it has the following

On R5:

 access-list 50 permit 226.0.0.0 1.255.255.255
 access-list 50 permit 228.0.0.0 3.255.255.255
 access-list 50 permit 232.0.0.0 3.255.255.255
 access-list 50 permit 236.0.0.0 1.255.255.255
 access-list 50 permit 238.0.0.0 0.255.255.255

on R1 it has

access-list 51 deny 224.0.0.0 1.255.255.255
access-list 51 deny 239.0.0.0 0.255.255.255
access-list 51 permit 224.0.0.0 15.255.255.255

Why cant we just put 226.0.0.0 12.255.255.255 as the access list for both
instead of writing them out the ways above?

I know there has to be a good reason and I just don't understand it though.

Dane



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