[lug] Learning about networking and firewalls?

[David Morris]

A cousin of mine is interested in learning more about networking,
specifically firewalls.  I've dealt with both for many years, but
picked up everything the hard way as I went along (by experimenting,
and occasionally making catastrophic mistakes).  The unfortunate
result is I have no reference material to point him towards, even
though I'm more or less an expert on the topic.

Anyone know of any good books or web sites to help him go through this
process a bit more easily than I did?

Thanks,

--David