Subject: [ssm] Dual homed multicast src and SSM

From: "Field, Brian" <[email-masked]>
Date: Tue, 12 Oct 2004 17:19:04 -0600

Consider a network operating in SSM and a dual homed multicast src
device.  Is there a standard way to setup the forwarding between the
routers and the src device to get the SSM trees built properly?  Seems
as if the device needs to eiter participate in routing and announce the
src IP or run something like HSRP.  Issues with these approaches?
Other options?

Thanks
Brian

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From: Marshall Eubanks <[email-masked]>
Date: Tue, 12 Oct 2004 20:11:07 -0400

Dear Brian;

Routers set up trees, not edge devices (such as sources).

Generally, by "dual homed" you mean "part of an Autonomous System /
PIM domain with connections to two or more other AS / PIM Domains."
This is done by routers, so if your source is _directly_ connected
to interfaces leading to other domains, it will have to act like a
router and send and receive
PIM control traffic.

However, generally sources are not directly attached to other domains, and
sources and receivers do not participate in PIM and MBGP control
traffic. The internal multicast routing
protocol takes care of the tree creation inside the domain, and PIM
and MBGP take care of the
tree creation between domains.

So, this does not seem like a problem to me - SSM introduces nothing
new to multicast routing. If am
am missing something, please let me know.

Regards
Marshall Eubanks

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From: Beau Williamson <[email-masked]>
Date: Wed, 13 Oct 2004 13:20:54 -0500

Brian,

There is nothing specific to SSM that would prevent the trees from being 
setup between one AS and another.  The fact that the source domain is 
dual-homed only means that there are two paths form where Joins can arrive 
(from other domains).  This is of course controlled with normal BGP metrics 
and is no different from hosts in other AS's wishing to "send" unicast 
traffic to the source host.

Beau