We are having 1841 router for service provider connetivity. ISP has asigned us a pool of 14 public address. One IP we want to dedicate for our e-mail server. And remaining we plan to be used by internal users to for internet browsing.
we have inside mail server as 172.30.1.1 mapped with first address in the pool service provider gave us. comamnd used is
ip nat inside source static 172.30.1.1 First_Address_ISP_Pool.
select fa0/0 ( connected to internal switch )
ip nat inside
select serial 0/1/0 ( connected to ISP router )
ip nat outside
so far so good !
next, if we put access list ( incoming directin ) on serial 0/1/0 that allows only 110 port on the First_Address_ISP_Pool. I think it will block anything else except this traffic.
then how do we allow other internal users to use the internet by remaining free public ip address. Or does router works like PIX which allows return connections which were initiated from inside. And for connections initiated from outside we use static comand to allow access to internal servers. (in PIX).In a nutshell we want internal users to access internet with free ip address and fix up one ip address for e-mail server which will be accessed on 110 port from outside world mail servers how do achieve this ? any link on cisco is highly appreciable !
Thanx in advance