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Date:      Mon, 15 Oct 2001 09:36:52 -0700
From:      Bill Fenner <fenner@research.att.com>
To:        deepika_77@yahoo.com
Cc:        freebsd-net@freebsd.org
Subject:   Re: mrouted 3.8(how to find multicast members??)
Message-ID:  <200110151636.JAA16632@windsor.research.att.com>

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> But the definition of threshhold TTL says that a
>incoming multicast packets will be forwarded out of an
>interface only if it has the TTL value >= threshold
>TTL of that interface. Am I right?

No.  Zero is special, and means do not forward.  If you have
the kernel source, check out the ip_mdq() function in
/sys/netinet/ip_mroute.c; the check is:

        if ((rt->mfc_ttls[vifi] > 0) &&
            (ip->ip_ttl > rt->mfc_ttls[vifi])) {

(the threshold > 0 and the TTL > the threshold -- note, >, not >=.)

  Bill

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