hi
hope u hve 2 ethernet ports in ur router one to connect ur adsl connecitivity and other one to connect ur local lan.
configure one of ur eth port which is connected to the adsl connecitivity with the ip given by the adsl provider.
int fastethernet 0/0
no shut
ip address x.x.x.x y.y.y.y
ip nat outside
then configure ur local ethernet with any of the private ip if u dont have public block alloted to u by ur SP.
in this case u need to enable NAT on both ur ehternet interface to have ur internet connecitivity thru.
interface fastetherenet 0/1
no shut
ip address a.a.a.a b.b.b.b
ip nat inside
after completing this
create access-list permiting ur local lan block if ur using NAT..
access-list 1 permit a.a.a.a b.b.b.0
ip nat inside source list 1 interface fastethernet 0/0 overload.
for more on NAT ty this
http://www.cisco.com/en/US/tech/tk648/tk361/tk438/tech_protocol_home.html
for more on Access lists try this
http://www.cisco.com/en/US/tech/tk648/tk361/tk821/tech_protocol_home.html
regds
