Our company has a Cisco 1721 router in which I have setup remote users IP Addresses in the router SDM firewall configuration to pass thru to our separate VPN server machine. The problem is my remote users' ISP's change their IP Addresses randomly which causes me to go back to the router and input the new IP so they can get connected. Is there a way to use the MAC ID of my users' machines instead of the IP Address? I read somewhere that it can be done using ACL, but not sure on how to go about doing that? Any help is greatly appreciated.