I was recently configuring IPv6 on a FreeBSD, following the Handbook. I found something that could be made clearer for a novice like me (coming to FreeBSD from Linux). I hope it makes sense. In the section 31.9.2 (Configuring IPv6) the configured network device is first referred to as "em0", but then as "fxp0" immediately after. I understand that these are shown in italics, denoting a changeable parameter, but I think many people may be confused by this. I would suggest phrasing the section slightly differently. For example, the first paragraph could start by saying "Let's assume that your network device is named 'em0'". Then the examples further below could refer to 'em0' instead of 'fxp0', maintaining consistency. I would have provided a patch for the appropriate Docbook source, but after spending an hour with it, I find myself unable to compile the source :-( Sorry!
A commit references this bug: Author: dru Date: Sat Jul 25 13:55:29 UTC 2015 New revision: 47078 URL: https://svnweb.freebsd.org/changeset/doc/47078 Log: Make interface naming consistent in this section. PR: 200501 Sponsored by: Essen DevSummit Hackathon Changes: head/en_US.ISO8859-1/books/handbook/advanced-networking/chapter.xml