Chapter 11. Getting the Information you need about the PPP server

Before you can establish a PPP connection with a server, you need to obtain the following information (from the sysadmin/user support people of the PPP server):-

• The telephone number(s) to dial for the service If you are behind a PABX. You also need the PABX number that gives you an outside dial tone - this is frequently digit zero (0) or nine (9).

• Does the server use DYNAMIC or STATIC IP numbers? If the server uses STATIC IP numbers, then you may need to know what IP number to use for your end of the PPP connection. If your ISP is providing you with a subnet of valid IP numbers, you will need to know the IP numbers you can use and the network mask (netmask). Most Internet Service Providers use DYNAMIC IP numbers. As mentioned above, this has some implications in terms of the services you can use. However, even if you are using STATIC IP numbers, most PPP servers will never (for security reasons) allow the client to specify an IP number as this is a security risk. You do still need to know this information!

• What are the IP numbers of the ISPs Domain Name Servers? There should be at least two, although only one is needed. There could be a problem here. The MS Windows 95 PPP setup allows the DNS address to be passed to the client as part of its connection process. So your ISP (or corporate help desk) may well tell you you don't need the IP address of the DNS server(s). For Linux, you DO need the address of at least one DNS. The linux implementation of PPP does not allow the setting of the DNS IP number dynamically at connection time - and quite possibly will never do so. Note: whilst Linux (as a PPP client) cannot accept the DNS address from a server, it can, when acting as a server, pass this information to clients using the dns-addr pppd option.

• Does the server require the use of PAP/CHAP? If this is the case you need to know the "id" and "secret" you are to use in connecting. (These are probably your user name and password at your ISP).

• Does the server automatically start PPP, or do you need to issue any commands to start PPP on the server once you are logged in? If you must issue a command to start PPP, what is it?

• Is the server a Microsoft Windows NT system and, if so, is it using the MS PAP/CHAP system? Many corporate LANs seem to use MS Windows NT this way for increased security.

Carefully note down this information - you are going to use it!