[mythtv-users] Ethernet troubles.

[Simon Hobson]

Ronald Frazier wrote:

>Just because NAT is used in combination with private addresses doesn't
>make it not "real" or "pure". It's still NAT, which simply means
>translating one address into another address. Either way it maintains
>the same style lookup table (address X maps to address Y). It just so
>happens that all of the addresses in one of the columns are the same
>address.

Actually, being vary pedantic, what you describe is not NAT - it is 
NAPT (Network Address and Port Translation). Pure NAT only does 1-1 
address mapping (leaving all port numbers unchanged) - so you need as 
many public IPs as you have internal devices you want to map for.

>That might not seem so obvious if you haven't actually used something
>like iptables, but once you have, it is glaringly obvious exactly how
>it is done. With iptables, it takes the exact same configuration
>commands to setup a 1-to-1 mapping as it does a 1-to-many mapping of
>addresses. The only difference is what you specify as the source and
>destination addresses in the configuration commands.

Which is not relevant ! It usually is very similar setting up NAT and 
NAPT (I have some experience across a number of vendors kit). IIRC in 
the IPTables world it's not even called NAT, but Masquerading.


NAT is yet another of those terms that has a very precise meaning, 
but is so regularly misused that the correct meaning is no longer 
recognised. 'RJ45' anyone ;-)

-- 
Simon Hobson

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