VxLAN needs port 4789, so if it can't bind to that, then that's a problem. What does: # netstat -tunlp | grep 4789 Show?
This seems to be a problem with the vxlan code in the kernel. It incorrectly fails if IPv6 is not configured. I'm trying to find the bug this is being fixed under. rhowe, do you know the bug number?
The kernel bug is: https://bugzilla.redhat.com/show_bug.cgi?id=1445054
*** This bug has been marked as a duplicate of bug 1445054 ***