PDF user manual for CopperEdge 150

3ODQQLQJWKH*GPWDQG*OLWH1HWZRUNAlthough the ADSL modules (both G.dmt and G.lite) support allnetmodels, we will discuss only two of them: Cross-Connect inPoint-to-Point Protocol (PPP) and Full IP. The two netmodelshave different capabilities and different requirements for configuringCE150s and CPEs.&URVV&RQQHFW1HWPRGHODQG3RLQWWR3RLQW3URWRFRORYHU$70If you have a LAN and a series of hosts downstream from yourCPE and if you have it configured in bridge mode, the Cross-Connect netmodel can be set up with either public or private IPaddresses for the hosts. In bridge mode, the CPE treats thehosts on the LAN as extensions of a subnet configured at theother end of the PPP connection. But, if you have a LAN andhosts downstream from your CPE and if you have it configuredin router mode, the setup is different. A CPE in router mode canfunction as a simple or a complex router, using a DHCP functionand a Network Address Translation (NAT) function.In simple router mode, the setup typically requires a public IPaddress for the CPE and the hosts. In complex router mode, thesetup typically requires an IP public address for the CPE. Usinga DHCP function, the CPE then dynamically assigns private IPaddresses to hosts on its LAN. When the hosts send messagesupstream, the CPE sets up a table, recording all source anddestination addresses. Then, before the CPE forwards packetsupstream to a destination, it substitutes its own public addressfor the hosts’ private addresses. In response, when messagescome downstream for hosts on the LAN, the CPE consults itsrouting table for source and destination addresses. Before itforwards packets downstream, it substitutes the hosts’ privateaddresses for its own public address.VC 23VC 130RouteTablesHOST1HOST2NAT &DHCPCPERouterCross-ConnectDSLAMRouteTablesTelcoRouterNY RouterRouteTablesSF RouterRouteTablesLA RouterCross-Connect Netmodel and Point-to-Point Protocol&RSSHU(GJH,QVWDOODWLRQDQG2SHUDWLQJ*XLGH