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Re: IPV6 renumbering painless?

  • From: Owen DeLong
  • Date: Sat Nov 13 02:54:31 2004


--On Saturday, November 13, 2004 2:56 +0100 Daniel Roesen <[email protected]> wrote:

On Fri, Nov 12, 2004 at 05:06:17PM -0800, Owen DeLong wrote:

> OK, but this doesn't have any effect on your "Listen",
> "NameVirtualHost" and "<VirtualHost>" statements of your httpd.conf,
> "ListenAddress" in sshd.conf, "Bind" in proftpd.conf, "*-source" and
> "listen-on*" in named.conf, [...]
>
True.  However, in all of the cases above except named.conf,
names are a perfectly valid substitute for the IP address.

No. Those configs are read at boot-time. Now think about a power
outage recovery. Server comes up but cannot reach DNS when services
are starting up. Boom, your server's services bail out and are dead
in the water. To prevent this, you might fill your /etc/hosts with
the own FQDN-to-IP mappings, but this again has the problem of being
pretty static.


Or... Recognizing that you have a dependency on DNS, you include
S10WaitForDns in your rc3.d and don't continue the bootstrap until
DNS is reachable.  Of course, if you're all _THAT_ worried about it,
you make your host a secondary for the domains it needs to know
about and have it run a caching resolver that is authoritative for
the local domains which only binds to the localhost port, so, no
problem and not static.  Then, you just need to start BIND before
you start those services.



> Not to forget all the IP address based ACLs.
>
I suspect that eventually, we will discover that ADDRESS-based
ACLs simply do not scale to a V6 world, and, you will see support
for other strategies, such as host-name based ACLs.

Layer 3 doesn't know host names. Nor does layer 4. Applications do.
Security requirements do often mandate working access control even
when DNS doesn't work or is compromised.


Security requirements are that you not permit packets that should not be
when DNS is not working.  Nothing says the router cannot run a resolver
pass when parsing the ACL or when told to refresh the ACL to translate
the configured names into IP addresses.  Nothing precludes a periodic
automatic refresh.

Hope this helps show that these problems can be mitigated in more
scalable ways.

Owen



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