| IPv6 Network - IFCONFIG: FRIEND OR FOE |
IPv6 Network - IFCONFIG: FRIEND OR FOE
People often assume that when someone has written a book about something, he or she knows a lot about the subject in question. I’m glad to say that this is generally indeed the case. After writing the book, at least. Authors discover many an interesting tidbit of information only during the writing process, which can be a humbling experience for those of us who think we knew everything already.
What I will take away from writing this book is knowledge of the proper ifconfig syntax. The first day at my first job in the Internet business, I impressed my new boss by reconfiguring an Ethernet interface on a SunOS machine with a new MAC address. Not all that impressive in and of itself, but the SunOS operating system had the strange habit of reprogramming all the Ethernet interfaces in a machine with the same MAC address. Because the server in question was connected to the same Ethernet with two interfaces, this meant that it would receive every packet twice (once on each interface), which didn’t exactly help performance. With different MAC addresses on both interfaces, the speed increased significantly. That day was probably the last time that I consulted the ifconfig man page, because I’ve been struggling with the command’s syntax ever since. I can never remember the order of the inet6 (no, not -inet6) argument and the add, delete, alias, -alias parameters and the like on various UNIX-like systems. So imagine my surprise when, after scrutinizing a rough draft of this chapter, Pim van Pelt (one of the two invaluable technical reviewers for this book) pointed out that the proper order is as follows: ifconfig [-L] [-m] interface [create] [address_family] [address[/prefixlength] [dest_address]] [parameters] So the correct syntax in Listing 3-16 wouldn’t be ifconfig gif0 inet6 delete 2001:600:8:34::2 (or ifconfig gif0 inet6 -alias 2001:600:8:34::2) but ifconfig gif0 inet6 2001:600:8:34::2 delete. I think I can remember that.
The moral of the story is that commands such as ip, ifconfig, route, and netstat are sufficiently complex and different between various operating systems that it pays to have a look at the man page when you need to do things that fall outside your everyday routine. Whether allowing different ways to achieve the same result is a good idea is a philosophical question. It is certainly confusing from time to time.
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