Re: *.G entry in Dense Mode,

Good Afternoon Roy,

In research that I did the following:
Dense mode will operate on a source based tree:

 (*, G) Entry - The (*, 224.1.1.1) entry shown in sample output of the show ip
mroute command is the (*, G) entry. These entries are not directly used for
multicast traffic forwarding in PIM-DM. However in Cisco IOS, all (S, G) entries
will always have a parent (*, G) entry and in the case of PIM -DM the OIL of
these entries reflect interfaces that:
 Have PIM -DM neighbors or
 Have directly connected members or
 Have been manually configured to join the group.

So even though you have dense mode configured you will have
cooresponding (S,G) entry with the IOS.

Multicast Forwarding
Forwarding of multicast traffic is accomplished by multicast-capable
routers. These routers create distribution trees that control the path
that IP multicast traffic takes through the network in order to
deliver traffic to all receivers.

Multicast traffic flows from the source to the multicast group over a
distribution tree that connects all of the sources to all of the
receivers in the group. This tree may be shared by all sources (a
shared tree) or a separate distribution tree can be built for each
source (a source tree). The shared tree may be one-way or
bidirectional.

Before describing the structure of source and shared trees, it is
helpful to explain the notations that are used in multicast routing
tables. These notations include the following:

(S,G) = (unicast source for the multicast group G, multicast group G)
(*,G) = (any source for the multicast group G, multicast group G)
The notation of (S,G), pronounced "S comma G," enumerates a shortest
path tree where S is the IP address of the source and G is the
multicast group address.

Shared trees are (*,G) and the source trees are (S,G) and always
routed at the sources.

http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_pim/configuration/12-4t/imc_tech_oview.html

Regards,
John

On 6/9/12, oo IPX <oispxl_at_gmail.com> wrote:
> it should help.
>
> https://learningnetwork.cisco.com/message/199281#199281
>
>
> On Sat, Jun 9, 2012 at 7:32 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar>
> wrote:
>
>> Some things are just because someone decided that this was the best way
>> to
>> do it, and you may not have all the data to "see" why it was so.
>> Unless you are a programmer and are trying to understand an
>> implementation
>> design decision: that's the way it is.
>>
>> Cisco IOS routers use a data model where some of the data of (S,G)
>> entries
>> is at the (*,G) entry. So even if it is not needed for the sake of the
>> protocol (PIM Dense), it is used.
>>
>> -Carlos
>>
>> roykhan123_at_hotmail.com @ 09/06/2012 08:30 -0300 dixit:
>>
>> Dear All,
>>>
>>> I need your help to understand in Multicast Dense Mode why the routers
>>> install
>>> *,G entry even they are also installing the S,G entry.
>>>
>>> I need to why this happening if i have 100 group it means that all the
>>> router
>>> in Topology 100 (*,S) and S,G entry
>>>
>>>
>>> thanks
>>>
>>>
>>> Br
>>>
>>> Roy
>>>
>>>
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>>>
>>>
>>>
>> --
>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>>
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> ______________________________**______________________________**
>> ___________
>> Subscription information may be found at: http://www.groupstudy.com/**
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>
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Received on Sat Jun 09 2012 - 12:34:30 ART