I use isdn with isdn-config from rawhide, glibc, Xfree86 isdn and kernel. When I use isdn-config with kernel 2.4.0-0.37 it can not load ippp0 devices. It does not exist according to isdn-config. Isdn-config states also that ppp is not compiled into kernel. When i use kernel-2.2.16-22 from Redhat linux 7.0 isdn-config work.
ppp is missing from kernel-2.4.0-0.37