Mailinglist Archive: opensuse (686 mails)

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Re: [opensuse] IPv6 - do you use SLAAC or DHCP ?
Per Jessen wrote:
As I mentioned, it's easy enough to add IPv6 addresses to DNS
But when they're randomly generated even for well-known clients, how is
my DNS updated?

There are two common ways to get an IPv6 address, as I mentioned in a
previous nete. There is one based on the MAC address and it is
permanent. Short of replacing the NIC, that address won't change. The
other is to use a random number, which does change frequently. It's
possible on both Linux & Windows and I expect Mac too, to enable either
or both methods. I didn't have to do anything special on Linux to get
both. They just work. On Window XP, they also just worked, but on
Windows 7, I had to specifically enable the MAC based address. Like the
link local address, the MAC based address will contain your MAC address,
but with FFFE inserted in the middle. With openSUSE you should have
both address types, assuming you have RADVD running somewhere to assign
the network portion of the address.

I would still like to be able to recognize them in logs etc. With
ip6?tables, tcpdump and such I'd also still want to recognize them in.
For a server that has nnn.nn.2.49 today, I was thinking of assigning
2001:db8:1020:ff1::1:2049 - no problem with DHCP6.

Once you've been working with them for a while, you'll soon recognize
the MAC based addresses.

On my network, I use the SLAAP addresses as mention. I use manual
configuration for anything that's permanently attached to my network,
for things like NTP & DNS server.
Okay. How do you prevent those servers from getting a randomly generated
IPv6 address?

You should have both MAC based and random addresses already. Just use
the MAC based for your servers. It doesn't matter about the random
number one, so long as your DNS or hosts file contain the MAC based. If
you have a random address, it's normally used for outgoing connections,
not incoming.

Run ifconfig to see your addresses. You should see a link local address
that starts with FE80:: and the right hand portion is your MAC address
with FFFE in the middle and the universal/local bit of the MAC
inverted. If you have a MAC based address, the host part of the address
will be identical to that of the link local address, but with the
network portion assigned by your router.. A random number address will
have the same network portion as the MAC address, but the least
significant 64 bits will be a random number and if your computer has
been up for a while there will be a few of them. The top one will be
the current, but the others are still valid, but deprecated.

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