[radvd-devel-l] advertise dns server with dynamic ip

[Erich Eckner]

Hi,

thanks for the help!

I'm not sure if Base6Interface is the right thing.
(I'll call my local interface eth1 and my external eth0).

The prefix and ip of eth1 get set by dhcp6c listening on eth0, so radvd
could just use this - which it does if "prefix ::/64" is specified
without any "Base6Interface" statement - but I can add a "Base6Interface
eth1;" line.
Okay, I just tried to insert "Base6Interface eth1;" which does not work
"automatically selecting the prefix and Base6Interface are mutually
exclusive". The problem with my isp is that I only get one external /128
IP for my router and may request several (non-consecutive) /64 prefixes
for my local subnets - that's the reason for me to let it assign by dhcp6c.

Regarding dns-advertisements:
Hmm, the link local address - I haven't thought of that! (Sry, I'm quite
new to IPv6, as I've said before). This should work in my case. But
wouldn't it prevent clients behind another router to use this dns
server? I know, that radvd won't advertise into the next link, but the
router which does would need to find out the dns server's global address
somehow or it would need to run a dns server itself ...

regarding mdns:
That sounds interesting, however, not applicable for me:

1st I want to be able to connect between clients of different local
links (eth1 is not the only local link) and therefore different
prefixes. With IPv4 I run a dns-server on my router and resolved
host.$mysearchdomain to the respective ips. (Routing between the local
links was activated, of course). Then something like "ssh user at host"
worked as expected.

2nd I really like running a separate dns server, because that way I can
enable dnssec within a trustworthy boundary and also define some
dns-level aliases for machines I often contact (no, an entry in
.ssh/config is not sufficient for what I want).

regards,
Erich

On 24.02.2017 15:03, Reuben Hawkins wrote:
> It sounds like you should use Base6Interface.  It works like this...
> 
> If your eth0 is your upstream interface connected to your ISP and your
> eth1 is connected to the rest of your local network, you would config
> radvd like so..
> 
> interface eth1 {
>   prefix 0000:0000:0000:0001::/64 {
>      Base6Interface eth0;
>      ...
>   };
> };
> 
> Then your prefix will be combined with the address on eth1 and the
> combined address will be advertised.  This assumed you get a /48 on eth0
> from your ISP.  If your /48 is 2001:db8:1234::/48, then the combined
> address for eth1 would be 2001:db8:1234:0001::/64.  If the address on
> eth0 changes, radvd should detect this and do the right thing.
> 
> Your DNS address needs to be fixed.  Just use eth1 link local address
> (fe80::something).  Your link local address should be fixed.  Also, use
> mdns and just connect to all your local machine using the .local suffix
> like so...
> 
> $ ssh user at remotehost.local
> 
> ...Much easier using mdns.  No server to configure.
> 
> On Wed, Feb 22, 2017 at 11:34 PM, Erich Eckner <radvd at eckner.net
> <mailto:radvd at eckner.net>> wrote:
> 
>     Hi,
> 
>     I'm currently enabling IPv6 on my home network. On my router runs debian
>     with routing via ip(6)tables, bind9 and radvd. The remote ip and the
>     global prefixes for the local interfaces are received via dhcp6c from my
>     ISP and may not always be the same.
> 
>     Now I've set up radvd to advertise routing and the prefixes on the local
>     interfaces via a "prefix ::/64" statement in /etc/radvd.conf. What I'd
>     like to do, is to announce the dns-server via a similar RDNSS statement
>     (e.g. "::1/64"). Is this possible somehow? Currently, I can only set a
>     fixed (the current) ip, but as I said before: This may change in the
>     future.
> 
>     I think, it won't be necessary for radvd to detect a change of the Ip
>     (although it would be nice), it would suffice (for me), if it can
>     determine the ip of some given interface - like it does with the
>     prefix-announcement.
> 
>     regards,
>     Erich
> 
> 
>     --
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>     <mailto:radvd-devel-l at lists.litech.org>
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> 
> 
> 
> 

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