How do I get fixed and dynamic ppp

root (
Tue, 14 May 1996 18:02:57 +1200 (NZST)

We run a small internet service here and have provided dialin ppp with an
assigned ip address based on the tty line one connects to using
/etc/ppp/options.ttyCxx files to assign the ip address. We now have a
customer who want to have a fixed ip address but starting up pppd with a
command line option doesn't seem to override
the equivalent in the options file. Has anyone got a clever solution?