i have two questions to ask

1) i am using dsl
the router dns is 10.x.x.x
and
isp dns is 203.x.x.x

for masquareding client need dns entry
now tell me which entry is better
for router dns entry or isp dns entry .

mean which provide better speed

from my point of view isp dns is better because router dns first convert 10.x.x.x to 203.x.x.x and then send dns query to isp. am i right ?

2) i want to to accept some mac addres from my clients on input chain as

iptables - A INPUT -m mac --mac-source x.x.x.x.x -j Accept
---------------------------- ----
-----

now i want to drop all others clients mac how can i do that

1-
i think that it wont matter.

2-
iptables -F INPUT
iptables -P INPUT DROP
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -m mac --mac-source x.x.x.x.x -j ACCEPT

good luck.