From: "Frank Haber" 

Some ISPs make a (usually desultory) attempt to charge you more if you have
a SOHO LAN attached, or make you rent their
cablemodem/router_with_optional_VOIP box.  They like to keep track of your
MAC, so they can charge you back, Jack.

I had a very weird experience three or four years ago trying to change the
MAC on an early Linksys (BEFSR41).  It absolutely would not register with
one ISP's devices.  I tried it at two customers.  I tried it with two
Linksys boxes.  Four permutations, carefully done.  No go.

When I went "native" on the Linksyses and begged the ISPs to
reset me, everything worked immediately.  I know little of the formatting
of a Mac at the hardware level, and less about any Linksys deficiencies,
but an ISP tech I met on the street said, "Oh yeah - MAC changing
doesn't seem to work."

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