This program does not have a useful manpage. When a manpage becomes available it will be included. If you are a competent and accurate writer and are willing to spend the time reading the source code and writing good manpages please write a better man page than this one. Please contact the package maintainer in order to avoid several people working on the same manpage.
You can start reading the very good documents available in the /usr/share/doc/iproute/ directory, in .ps, .dvi and .tex formats.
In particular, you can find the IP command reference manual in the /usr/share/doc/iproute/ip-cref.* files.