IPv6 Conventions

Owen DeLong owen at delong.com
Thu May 19 07:46:16 UTC 2011

On May 19, 2011, at 12:05 AM, Iljitsch van Beijnum wrote:

> On 19 mei 2011, at 5:21, Owen DeLong wrote:
>>>> 2) Are we tending to use different IPs for each service on a device?
>>> No, the same Internet Protocol.
>> I believe he meant different IP addresses
> No, that can't be, he would have said "IP addresses".

No, it is not uncommon at least in America for people to refer to IP addresses by the shorter
term "IPs".

>> and I highly recommend doing so.
>> If you do so, then you can move services around and name things independent of
>> the actual host that they happen to be on at the moment without having to renumber
>> or rename.
> The DNS is already a layer of indirection so in most cases this makes things harder first (having to remember which address is on which host) so they may be easier later (not touching the DNS when services go to a new box). In my opinion, this isn't a good tradeoff most of the time. Only if you want/need addresses to be a particular way (like short for DNS servers) that's helpful.

We can agree to disagree. You need to remember which box your particular
services are on anyway, so, I don't see much difference there. Often, the time
delay in DNS changes can be a blocking factor in addressing load issues
by moving things around quickly. IP addresses can be moved with much
greater agility than the DNS abstraction because there are too many broken
browsers and such out there (thank you Micr0$0ft) with ridiculous tendencies
to cache DNS information for a very long time (well beyond the TTL).

> I was reluctant to do stateless autoconfig for servers at first but it's really rock solid, as long as you're reasonably sure no rogue router advertisements will show up on the subnet in question there's no reason to avoid it.

Well, there is one reason... If you have to swap a NIC or any superset of 
a NIC such as an entire machine, you'll have to update
DNS. If you forget to do the DNS update in such a circumstance, you
can blackhole a lot of traffic in the time it takes to figure that out.


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