Multicast

Unanswered Question
Feb 23rd, 2009
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QUES:

Configure R2 as the RP for the multicast group 227.7.7.7

R5 should be the RP for all other multicast groups.



ANS:

1. access-list 10 permit 227.7.7.7

2. access-list 11 deny 227.7.7.7

3.access-list 11 permit any


ip pim rp-address 10.1.2.2 10

ip pim rp-address 10.1.5.5 11


Note:

R2 ip address is 10.1.2.2

R5 ip address is 10.1.5.5


According to the above PIM question,since there is an exclusive deny at the end of all access-list (10) statement, is the second line of the access-list needed?

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Harold Ritter Mon, 02/23/2009 - 07:33
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The second line is actually for ACL 11, not ACL 10.


The logic for ACL 11 is to first deny group 227.7.7.7, which is taken care of by R2 and then accept everything else.


Regards

Just Kennie Tue, 02/24/2009 - 10:08
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But since access-list is executed in branches,then group 227.7.7.7 would have been taken care of by access-list 10 and it wont get to the second statement....Is the second statement still neccessary ?

Jon Marshall Tue, 02/24/2009 - 10:17
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As Harold has pointed out the deny statement is part of acl 11.


You are correct in what you say about lines within an access-list being executed in order but this doesn't apply to different access-lists ie. without the deny line at the start of acl 11 then R5 would become the RP for 277.7.7.7 as well.


Jon

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