Advanced network config:
There are two other network settings, but no one reads this text so there's no reason to tell you about them. In case you actually do read this, here's the deal: by default, I2P will attempt to guess your IP address by having whomever it talks to tell it what address they think you are. If and only if you have no working TCP connections and you have not overridden the IP address, your router will believe them. If that doesn't sound ok to you, thats fine - go to the advanced config page and add "i2np.tcp.hostname=yourHostname", then go to the service page and do a graceful restart. We used to make people enter a hostname/IP address on this page, but too many people got it wrong ;)
The other 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.