[dns-operations] Link-local IP addresses for a resolver?

Mark Andrews marka at isc.org
Tue Sep 24 22:54:28 UTC 2019

> On 25 Sep 2019, at 6:13 am, John Levine <johnl at taugh.com> wrote:
> In article <alpine.DEB.2.20.1909242008320.23255 at grey.csi.cam.ac.uk> you write:
>> Florian Weimer <fw at deneb.enyo.de> wrote:
>>> We added scope ID support to /etc/resolv.conf in upstream glibc a
>>> couple of years ago, in 2008.  I can easily see that others may not
>>> have done this, so I agree that there could be problems.
>> I did a bit of a survey in 2014 and found that prominent DNS
>> libraries didn't support link-local addresses back then
>> http://lists.cluenet.de/pipermail/ipv6-ops/2014-July/010035.html
>> Maybe it's better now :-)
> How are they with RFC 4193 ULAs?  I've been using a cache at a ULA on
> my two-segment home network and it seems to work fine.
> (And why would you use link local rather than ULA for your DNS resolver, anyway?)

ISP’s advertings ULA’s to customers have similar problems with advertising LL to customers.
The CPE should be the site boundary making the ISP’s DNS servers unreachable from inside the
customer’s network.

DNS servers that are expected to be reached across sites need to be globally unique addresses
which ULA and LL are not.


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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka at isc.org

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