I have a 1721 cisco router with one adsl wic installed.It has a wan address with we want to change because our ISP needs to change ....
Using SDM , which is the best way to do?If I change the ip using SDM the router will change my nat configuration from the older WAN address to the new??
You can check out whether your actual NAT/PAT statement pointing out your interface or the ip configured on your interface.
If its pointing towards your interface i dont think you really need to change anything on the nat statements.
Also i feel your SP might have provided dynamic ip which may change time to time whenever you get connected..