My understanding of EIGRP multicast packets was that the TTL is set to
one, and that this is the mechanism that prevents the packet from being
routed off the local subnet.

However, doing a packet capture reveals that the TTL on EIGRP multicast
packets is actually 2. Some research hints that the same may be true for
RIP and OSPF, although I haven't verified. The Wireshark expert note
refers to RFC 3171, but that RFC doesn't mention TTL. Here is the actual
text of the note:

"Time To Live" != 1 for a packet sent to the Local Network Control Block
(see RFC 3171)

So what is the purpose of setting these TTL's to 2? Obviously, they are
not getting routed off the subnet, so some other mechanism is being used
to prevent this.

Thanks,

Doug
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