Bay Networks 5390 Administering page 169

Communications server

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This chapter describes the Model 5390 implementation of the standardized method for transmitting

datagrams from multiple protocols over serial point-to-point links. PPP provides three functions:

Asynchronous High-level Data Link Control (HDLC) to encapsulate the packets.

Link Control Protocol (LCP) to establish the connection between peers.

A family of Network Control Protocols (NCPs) to conﬁgure network interfaces.

PPP allows a site to use the Model 5390 server as a wide area network (WAN) hub, tying distant

corners of an IP network together over low cost phone lines. PPP features include:

FCS error checking.

Agreement by each end of the connection on a mutually acceptable set of features for that

Large Maximum Receive Unit (MRU) size—negotiations start

In setting up a PPP link:

You can attach a PC to the Model 5390 serial port. Using PPP as the network interface, the PC

becomes a host on the network. For a remote PC with a PPP client that supports scripting, you

can conﬁgure a port in CLI mode. Then, a user at a remote PC can dial into the Model 5390

server using a modem and convert the port from a CLI to a PPP link using the CLI ppp

command. After converting the port to a PPP link, the remote PC becomes a host directly

attached to the network.

Alternatively, you can set the Model 5390 port to auto_detect or auto_adapt. When the

Model 5390 server detects the PPP protocol on the line attached to the port, it automatically

converts the port mode to PPP and starts LCP negotiations.

If your PPP client is expecting to connect to a server already in ppp mode, the Model 5390

port's mode must be ppp, auto_detect, or auto_adapt.

You can use PPP to connect two separate networks, routing data from one network to the other

over the PPP link.

Point-to-Point Protocol (PPP)

NOTE: The Model 5390 server cannot boot over a PPP link.