.:Computer Defense:.

I always base the quality of my week on what I've learned... It's not the only criteria obviously but it is one of them... If I've learned nothing then the week seems like a total waste... yet if I learn just one or two things... even if they are common knowledge to everyone else... as long as they are new to me... I'm excited. There's something about learning these little tidbits... Random information that was out there for the taking that you'd just never looked into before.

So what did I learn this week?

I learned how to devise a link-local address in IPv6. I had originally thought it was only Microsoft's method due to some misinformation on a website, however I was pointed to the RFC that shows it is the method for creating it. So I guess I learned two things... kinda.

Method:

1. Take the MAC address. - 00-0C-F1-EB-F0-43
2. Insert FF-FE between the third and fourth bytes. - 00-0C-F1-FF-FE-EB-F0-43
3. Complement the second low order bit of the first byte. - 02-0C-F1-FF-FE-EB-F0-43 (known at this point as the Interface Identifier)
4. Combine the prefix (FE80::/64) with the interface identifier. - FE80::20C:F1FF:FEEB:F043

The IPv6 link-local address is FE80::20C:F1FF:FEEB:F043

The other interesting tidbit I picked up was that egrep on older systems didn't support curly braces {}.  Since most of my regex experience has come from Python, I actually use curly braces a fair amount. I decided to test this and sure enough on Solaris 6 (for example), curly braces don't work.

# echo 'AAAAA' | egrep 'A{4}'
#

Yet on a fairly up-to-date FreeBSD system:

$ echo 'AAAAA' | egrep 'A{4}'
AAAAA

Anyways, just thought I'd share those.... Now maybe you've learned something new this week... Enjoy!