Addressing
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... those with "1111" as their high-order four bits, are reserved for
future addressing modes.
In Internet standard ...
... Host group addresses cannot, however, be used to solve all problems
of internetwork logical addressing, such as delivery to the "nearest"
or the "least loaded" network interface ...
... routing option, be accepted without
complaint, thereby allowing other implementations to experiment with
logical addressing applications of host group addresses.
...