Question : Problem: wan ip

How to setup a dns to send mails internally to other server.

Answer : Problem: wan ip

Hi there

Use the ip accounting feature in the interface configuration mode:
Router#config t                          
Router(config)#int s0                  (or the ethernet interface-depends what you want to know)
Router(config-if)#ip accounting  

Then you use the "show ip accounting"  command to see what ip addresses passsed packets over the interface.
Router#show ip accounting      

This is almost like a debug command and should not be left on too long as it could bring down a heavily utilised router if it runs out of memory.
Remember to go back into interface config mode and disable it wit the "no ip accounting" command.
Router(config-if)#no ip accounting  

Hope this helps
Nic