Chapter 25. After the link comes up - the /etc/ppp/ip-up script

Table of Contents
25.1. Special routing
25.2. Handling email queues
25.3. A sample /etc/ppp/ip-up script
25.4. Handling email

Once the PPP link is established, pppd looks for /etc/ppp/ip-up. If this script exists and is executable, the PPP daemon executes the script. This allows you to automate any special routing commands that may be necessary and any other actions that you want to occur every time the PPP link is activated.

This is just a shell script and can do anything that a shell script can do (i.e. virtually anything you want).

For example, you can get sendmail to dispatch any waiting outbound messages in the mail queue.

Similarly, you can insert the commands into ip-up to collect (using pop) any email waiting for you at your ISP.

There are restrictions on /etc/ppp/ip-up:-

25.1. Special routing

If you are linking two LANs, you will need to set up specific routes to the 'foreign' LANs. This is easily done using the /etc/ppp/ip-up script. The only difficulty arises if your machine handles multiple PPP links.

This is because the /etc/ppp/ip-up is executed for EVERY ppp connection that comes up, so you need to carefully execute the correct routing commands for the particular link that comes up - and not when any other link comes up!