Based on ELREPO http://elrepo.reloumirrors.net/kernel/el6/SRPMS/
with custom kernel config changes

Kernel config should consist following kernel options included:
CONFIG_L2TP=m
CONFIG_L2TP_IP=m
CONFIG_L2TP_ETH=m
CONFIG_L2TP_V3=y

To build i686 under x64 platform use 
rpmbuild -bb --target i686 /root/rpmbuild/SPECS/kernel-ml-3.10.spec