>1. Is the MAC address returned with ARP the actual 
>    server, or is it a computer between the router and the server?

There are some routers that do proxy arp by default. Check your router config.


>3. How often should I use ARP to get a new address?  I 
>imagine that unless the internet breaks, the server computer 
>is replaced or similar, that the MAC will remain the same.  
>Should I just ARP once and store it in eeprom, or when 
>the server stops talking for a period of time, or at every 
>power cycle, or once/day...?  What is "standard"?
>

Run an "arp -a" on a PC or Unix box. This show the contents of the arp cache.
Most are dynamic entries that have a default life - some unix servers are 20 minutes.
Check the man page for arp to see examples of using static arp entries.


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