kernel too old from boot PXE

Hello,

I have a PXE boot server in linux and I try to initiate an automatical redhat installation.
the target version is RHEL 6.6 (in RHEL 7.2 work fine)
during the boot, I have this error message : kernel too old

however i used the vmlinuz file from rhel6.6 iso.
I try with a vmlinux version rhel7 but I have a fatal error.
Same error in VM and Physical server.

sorry for my English and thanks for your help