Advanced network config:
One advanced network option has to do with reseeding - you should never need to reseed your router as long as you can find at least one other peer on the network. However, when you do need to reseed, a link will show up on the left hand side which will fetch all of the routerInfo-* files from http://dev.i2p.net/i2pdb/. That URL is just an apache folder pointing at the netDb/ directory of a router - anyone can run one, and you can configure your router to seed off an alternate URL by adding the java environmental property "i2p.reseedURL=someURL" (e.g. java -Di2p.reseedURL=http://dev.i2p.net/i2pdb/ ...). You can also do it manually by getting routerInfo-*.dat files from someone (a friend, someone on IRC, whatever) and saving them to your netDb/ directory.
With the SSU transport, the internal UDP port may be different from the external UDP port (in case of a firewall/NAT) - the UDP port field above specifies the external one and assumes they are the same, but if you want to set the internal port to something else, you can add "i2np.udp.internalPort=1234" to the advanced config and restart the router.