Mailinglist Archive: opensuse (686 mails)

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Re: [opensuse] IPv6 - do you use SLAAC or DHCP ?
Per Jessen wrote:
Yes, I do. Not all systems got both types though. When a system is
assigned both, which one is used for outgoing connections?

The random address.


When I started radvd on the router/firewall, most of my systems only had
one address, the MAC-based one. I would not want the random address
used for outgoing connections though. (for arbitrary clients yes, but
not for anything fixed). I mean, imagine a mailserver delivering
outgoing mail from a random address??

Think of outgoing as you using a browser and incoming, your servers. It
is only the incoming traffic that needs to know the address. So, look
up your MAC based address and use it for your DNS. For outgoing, it
really doesn't matter which you use. There's a way to turn off random,
but I don't recall the details at the moment.


Hmm, so with SLAAC, systems are assigned an address based on the MAC of
the interface. That doesn't change so I can set up the DNS based on
that. Do you know how I can prevent the random address from being
used/allocated? It's possible that most of our systems are too old
(pre 12.x) for the random address to work, but with 13.1M2 I got this:


2: enp3s1f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state
UP qlen 1000
link/ether 00:15:60:57:07:f1 brd ff:ff:ff:ff:ff:ff
inet 192.168.2.140/21 brd 192.168.7.255 scope global enp3s1f0
valid_lft forever preferred_lft forever
inet6 2001:db8:2010:1ff:a5e4:4fb7:2ef0:5d1b/64 scope global
temporary dynamic
valid_lft 557201sec preferred_lft 38201sec
inet6 2001:db8:2010:1ff:215:60ff:fe57:7f1/64 scope global dynamic
valid_lft 2550353sec preferred_lft 563153sec
inet6 fe80::215:60ff:fe57:7f1/64 scope link
valid_lft forever preferred_lft forever


"fe80::215:60ff:fe57:7f1/64 scope link" is your link local address. That will
never change, unless you replace the NIC.

"2001:db8:2010:1ff:215:60ff:fe57:7f1/64 scope global dynamic" is your MAC based
address. Use this in your DNS.

In both of the above, you'll see your MAC address with FFFE inserted in the
middle, as well as the 2 in the first part of the host address. That 2 is due
to the universal/local bit being inverted. This is done so that if you create
local addresses, you don't have that bit on, making the address a bit simpler.

"inet6 2001:db8:2010:1ff:a5e4:4fb7:2ef0:5d1b/64 scope global temporary
dynamic" is your random number address. As you get more, all but the
lastest will say "temporary deprecated dynamic". I've got 3 of those.

I don't recall which version of openSUSE the random numbers started
with, but, IIRC, they weren't there 3 years ago.


As I mentioned, don't worry about that random address. It will be used
only when you are accessing something else from your computer. Just use
the MAC address in your DNS and you'll be fine.

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