SmartSwitch Router User Reference Manual 345Chapter 25: WAN Configuration GuidePoint-to-Point Protocol (PPP) OverviewBecause of its ability to quickly and easily accommodate IP and IPX protocol traffic, Point-to-Point Protocol (PPP) routing has become a very important aspect of WANconfiguration. Using PPP, you can set up router-to-router, host-to-router, and host-to-hostconnections.Establishing a connection in a PPP environment requires that the following events takeplace:• The router initializing the PPP connection transmits Link Control Protocol (LCP)configuration and test frames to the remote peer to set up the data link.• Once the connection has been established, the router which initiated the PPPconnection transmits a series of Network Control Protocol (NCP) frames necessary toconfigure one or more network-layer protocols.• Finally, when the network-layer protocols have been configured, both the host andremote peer can send packets to one another using any and all of the configurednetwork-layer protocols.The link will remain active until explicit LCP or NCP frames instruct the host and/or thepeer router to close the link, or until some external event (i.e., user interruption or systemtime-out) takes place.You can set up PPP ports on your SSR with the commands described in Chapter 32: “portCommands” in the SmartSwitch Router Command Line Interface Reference Manual.Use of LCP Magic NumbersLCP magic numbers enable you to detect situations where PPP LCP packets are loopedback from the remote system, resulting in an error message. The use of LCP magicnumbers is enabled on the SSR by default; however, should you employ a service profilein which the use of LCP magic numbers has been disabled, undetected “loopback”behavior may become a problem.Note: In the event that a PPP WAN interface remains unrecognized at startup due toloopback interference, you can use the ppp restart command in the CLI to remedythe situation.Configuring PPP InterfacesThis section provides an overview of configuring a host of WAN parameters and settingup WAN interfaces. When working in the PPP environment, you must first define thetype and location of your WAN interfaces. Having established the type and location ofyour WAN interfaces, you need to (optionally) define one or more service profiles for your
