IP Vs DNS

[Barry Fawthrop]

Greetings all

with an IPTABLES ruleset you can specify an IP address to be allowed/blocked
iptables INPUT -s 12.12.12.12 -j ALLOW

But can this be done with a DNS name
iptables INPUT -s www.name.com -j ALLOW

since 12.12.12.12 may be www.name.com but it can also be
12.12.15.12 or 12.15.12.19
eg www.nasa.gov this address does vary depending on location and 
sometimes time of day
from a single point I can ping www.nasa.gov and get different IP 
addresses for it.

Yet I would like to allow access but preferably not to a whole range.
Also by allowing a DNS name then if a single IP addresses hosts many 
sites, I can be specific about the site?


Thanks in advance
B


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