Generate EUI-64 automatically when manually assigning prefix in Linux

[tedllewellyn]

  Is there a way to have Linux generate the EUI-64 portion of the local address when the prefix is manually assigned?  I am aware of the shell scripting tricks, but I'm looking for something that I could use in /etc/network/interfaces that would turn a static assignment of the prefix into the full link address.  The context is that the box is a router; all the other boxes autoconfigure.

[cholzhauer]

FreeBSD will do this if you give it the /64 it's supposed to use...what do you have in /etc/network/interfaces?

[tedllewellyn]

FreeBSD will do this if you give it the /64 it's supposed to use...what do you have in /etc/network/interfaces?

Nothing, yet (I'm using a script).  None of the docs I've seen seem to mention setting up anything but the tunnel interface.  I was trying to get more info.  Guess I'll just have to try it and see if they copied the functionality from FreeBSD and didn't bother to tell anyone about it.

[cholzhauer]

i doubt they copied freebsd :)  what distro are you using?

[jimb]

You can use ipv6calc.  Something like:

ipv6calc --in prefix+mac --action prefixmac2ipv6 --out ipv6addr 2001:db8::/64 00:01:02:6D:5A:A4
2001:db8::201:2ff:fe6d:5aa4/64


Just pull the MAC from ifconfig or ip link show or whatever.  I think there may be a way of specifying and interface and having it do it itself too.  EDIT: actually there isn't ... not sure where I got that idea from.  But it's fairly trivial to pull the mac and prefix out of whatever. 

[tedllewellyn]

i doubt they copied freebsd :)  what distro are you using?

Debian.

You can use ipv6calc. 

I know about ipv6calc.  I'll have to look at whether it will work the way I want it to.  Right now I'm just using a modified version of HE's script in rc.local.  In Debian terms this is a kluge.  Using ipv6calc probably is to.
I've been playing with firewall rules so I haven't had time to mess with this.

[jimb]

Well, why do you want a EUI-64 address on a router?  Typically, most people use low IPv6 address (like ::1) for routers.  If you're statically assigning something like that, it's simple to do in interfaces.

But if you insist, you might want to look in /usr/share/doc/ifupdown/examples/ for pre-up scripts and stuff which could do this for you.  That'd be "proper".

[snarked]

Maybe he wants to hide the fact that it's a router?

When you see a "...::1", don't you think that there's something else behind it?

[tedllewellyn]

Well, why do you want a EUI-64 address on a router?  Typically, most people use low IPv6 address (like ::1) for routers.  If you're statically assigning something like that, it's simple to do in interfaces.

Du-u-u-h-h-h!  That would make the packet traces a lot easier to follow, too, wouldn't it?  OK, someone whack me in the head for missing the obvious.

But I will look at the /usr/share/doc... material.  Sometimes there's good stuff squirreled away in there.

[jimb]

Maybe he wants to hide the fact that it's a router?

When you see a "...::1", don't you think that there's something else behind it?

Always possible, which is why I asked why he wanted to do it.  I suppose there are cases where you might want to "hide" a router from outside by putting it at some odd IPv6 in a /64, and preventing traceroute from working, etc.

Well, why do you want a EUI-64 address on a router?  Typically, most people use low IPv6 address (like ::1) for routers.  If you're statically assigning something like that, it's simple to do in interfaces.

Du-u-u-h-h-h!  That would make the packet traces a lot easier to follow, too, wouldn't it?  OK, someone whack me in the head for missing the obvious.

But I will look at the /usr/share/doc... material.  Sometimes there's good stuff squirreled away in there.

I was wondering if you had some reason for wanting to do it like that but I guess not.  :)  Obviously, it's not mandatory to use an MEUI-64 for your host address.  It's just what autoconfig uses.  You should use a /64 though, since that's what seems to be recommended if not mandated (there's a huge thread on the ipv6-ops list right now about whether it's "proper" to use longer-than /64 prefix lengths for things like p-t-p interfaces, such as /127s, /126s, etc.  Pretty lively debate.)