I have a DSL with 6 public IP addresses. I laready confirmed that the ISP can send the entire block to my cisco 871 router. I would like to distribute those IP's only to certain devices and certain devices have LAN IP's how can I have the 871 respond to two IP blocks and route correctly.
John has correctly identified one of the options, which is to assign the second address block as a secondary address on the router interface. Another option which you should consider is to use the address block to configure a pool of addresses for address translation. If you configure static address translation for some of the devices inside your network then these devices become accessible from the public Internet as well as being able to send traffic out to the public Internet using a public IP address as the source address.