When I install vpp and vpp-plugins:
Sudo yum install vpp
Sudo yum install vpp-plugins

in a fresh 64 bit Centos (http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-Minimal-1511.iso ):
uname –r
3.10.0-327.e17.x86_64

The plugin libs end up in /usr/lib64/vpp_plugins instead of /usr/lib/vpp_plugins

When running “vpp unix interactive” I can see that VPP is looking for the plugins at /usr/lib/vpp_plugins and does not find/load them then.

Quickly tried to copy the libs from lib64/ to lib/ and all worked as expected.