Subject: Re: windows / win95 / nt MBONE applications

From: "Jeffrey S. Curtis" <[email-masked]>
Date: Mon, 2 Dec 1996 01:46:30 -0600

Dino writes:
}    There is by just joining a group via the "ip igmp join-group <group>"
}    command. However, we don't multicast forward on the interface. 
}
}    What is the harm running PIM on an async interface that connects to
}    a host. There are 30-second periodic Querys sent but that is pretty
}    negligible.

The harm is that on generic dialin lines, you don't have any guarantees
that your async interface is being connected-to by just a dumb host.
This is especially true of a traditional LAN internetwork - if I have a
cisco connecting to a stub LAN, I always use "passive-interface" inside
the OSPF configuration to make sure that the users don't hook up some
OSPF-speaking device and do weird things (steal address space, inject
default, etc.).  For these same sorts of reasons, it would be nice to
have a parallel "passive-interface" command under PIM to specify that
these stub LANs (or async lines) should be considered under multicast
routing, but no neighbors should actually be solicited on the LAN (or,
as someone else indicated, have a separate command to enable just IGMP,
since PIM isn't really doing the "routing" for the LAN anyway).

Jeff
-- 
Jeffrey S. Curtis                      | Internetwork Manager
Argonne National Laboratory            | Email: [email-masked]
9700 South Cass Avenue, ECT-221        | Voice: 630/252-1789
Argonne, IL 60439                      | Fax:   630/252-9689

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From: Dino Farinacci <[email-masked]>
Date: Mon, 2 Dec 1996 09:45:51 -0800

>> that your async interface is being connected-to by just a dumb host.

    The cisco knows due to the fact that it doesn't receive PIM queries/hellos
    or DVMRP probes/reports.

>> since PIM isn't really doing the "routing" for the LAN anyway).

    You can do that today by not accepting any DVMRP neighbors and filtering
    PIM queries using input access-lists. 

    Nonetheless, point taken. Thanks for the input.

Dino