This tip explains howto setup ntop version 2.0 on OpenBSD 3.7 (it should work on the latest OpenBSD version as well) I know ntop version 2.0 is much older than the latest version but this is the latest version I have been able to integrate with OpenBSD.

First install the gdbm library:

# cd /usr/ports/databases/gdbm

# make && make install

Create the directory where ntop will store its database information:

# mkdir /usr/local/var/ntop

Download, extract, configure and make ntop 2.0:

# cd /tmp

# lynx -source http://packetstormsecurity.org/sniffers/ntop/ntop-2.0-src.tgz|tar xzfvp -

# cd ntop

# ./configure --with-gdchart-root=../gdchart0.94c

# gmake

# gmake install 

Start the ntop webserver on port 3000:

# ./ntop -w 3000 -d

Connect to the server running ntop from a client computer:

http://[ip address of ntop server]:3000/