The isdn4k-utils-3.1-22.i386.rpm contains a ipppd which contains a bug.
ipppd may claim "ioctl(SIOCADDRT) device route (ippp1/10.10.10.0/ffffff00):
File exists" on the dialed server which results in "IPCP terminated by peer
(sifaddr failed) on the dialing side. This is not consistent with the ipppd
source-code in isdn4k-utils-3.1-22.
It is consistent however with isdn4k-utils-3.0beta2; in this version
sys-linux.c, in sifaddr assumes an error if ioctl(SIOCADDRT) results in
Rebuilding the SRPM (3.1-22) fails on iprofd which can't find certain
macro's. Skipping iprofd during build results in a correctly operating
ipppd in the RPM. So I guess that isdn4k-utils-3.1-22.i386.RPM was shipped
with an earlier ipppd binary because it wasn't rebuilt.
It was fixed in Beta4.