From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Sat Sep 09 2006 - 19:09:52 ART
Hafi,
The multicast source does not need to have unicast reachability
to the unicast destination. This is because it is not sending packets
to the unicast destination, but instead just a multicast group address.
All the devices in the transit path will need a route back to the
multicast source to perform an RPF check. In the case of icmp pings the
final destination that joined the group will need a unicast route back
to the source in order to send the reply. Turn off "ip mroute-cache" on
the incoming multicast interfaces and look at the "debug ip mpacket"
output on a hop by hop basis to see exactly what is going on with the
multicast forwarding.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Hafizur Rahman (UK)
> Sent: Friday, September 08, 2006 7:13 AM
> To: ccielab@groupstudy.com
> Subject: multicast - ip igmp join group
>
> Hello
>
> I am trying to understand how Ping response to an ip igmp
> joing-group
> multicast group works. I have got following setup
>
> R1
> - FR hub -- Ip pim send rp announce loop0 --- ip pim
> send-rp-discove
> loop0
>
>
> R2 R3 -- E0 -- ip pim spares-mode
> Ip add 200.20.10.1
> Ip igmp join group
> 227.1.1.1
>
>
> R1 is FR hub and R2 and R3 are spoke. R1 is RP and also
> mapping agent.
>
>
> My question is in order for R1 and R2 to ping this M G
> 227.1.1.1 , do
> they need to have L3 reach ability to the int e0 unicast ip
> address
> 200.20.10.1
>
> In my lab it works with or with out L3 reach
> ability to add 200.20.10.1
>
> If R2 do not know how to reach 200.20.10.1
> then how can it ping this MG
> 227.1.1.1
>
> Any idea.
>
> Your help will
> be highly appreciated
>
> Thanks
>
> Hafi
>
>
> Sheikh Rahman
> Support Engineer
> Dimension Data United Kingdom
> Dimension Data House
> Building 2 , Waterfront Business Park
> Hampshire GU51 3QT
> +44 12 5277 9330
> Office
> +44 12 5277 9010 Fax
> hafizur.rahman@uk.didata.com
>
> For further
> information about Dimension Data, please go to
> www.dimensiondata.com
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This archive was generated by hypermail 2.1.4 : Sun Oct 01 2006 - 16:55:40 ART