python-netaddr is not currently being built for EL-5. If possible, please provide an EPEL package for EL-5.
There's been a python-netaddr package for EPEL for some time... https://koji.fedoraproject.org/koji/buildinfo?buildID=110429 http://download.fedora.redhat.com/pub/epel/5Server/x86_64/python-netaddr-0.5.2-1.el5.noarch.rpm