PDF user manual for CopperEdge 150

,31HWPRGHOIf you have a LAN and a series of hosts downstream from yourCPE and if you have it configured in router mode, the IP netmodelcan be set up with public IP addresses or private IP addressesfor the hosts. In router mode, the CPE treats all of thehosts on the LAN as extensions of a subnet configured on theCE150.But, if you have a LAN and a series of hosts downstream fromyour CPE and if you have it configured in bridge mode, the setupis different. A CPE in bridge mode also can be set up witheither public or private IP addresses for hosts.In bridge mode, hosts on a LAN use a DSL port on the CE150as a gateway. Once packets arrive at a DSL port, the CE150looks up its default IP route and sends them to a WAN VC. Itforwards them over a Point-to-Point link to a Telco router. If thepackets have been sent by hosts with public addresses, therouter sends them out over the Internet to a destination addresswith their source address embedded.If the packets have been sent by hosts with private addresses,the Telco router uses its NAT function and replaces the privateaddresses with its own public address. Then the router sendsthe packets out over the Internet to their destination with itspublic address (or source address) embedded. In response,when messages come downstream for hosts on the LAN, therouter looks through its routing tables for the private addresses(or destination addresses). Before the router forwards the packetsdownstream, it replaces its own public address with the appropriateprivate addresses for the hosts.IP Netmodel&KDSWHU$'6/*OLWHDQG*GPW