Richard,
appreciate any thoughts on how to determine what is bringing the link up and how to stop it coming up when not required.
Use iptables to log all the packets that come into the interface
iptables -A INPUT -p ALL -j LOG --log-prefix "PACKET:" then troll through the log greping for "PACKET:" and figure out which packet coincides with the time the modem dialed. I think you will find that your little windoze boxen are very verbose and keep sending net-bios infomation. You want to block this. Also they tend to keep asking for DNS resolves, which is bloody difficult to block because you don't know when they should or shouldn't be asking. I don't know much about the demand option with pppd, I use diald which has a filter file into which you put which protocols pull the link up and for how long, I imagine that pppd -demand has a similiar filter file somewhere. If not then ditch it and install diald. HTH Pete -- SLUG - Sydney Linux User's Group - http://slug.org.au/ More Info: http://lists.slug.org.au/listinfo/slug
