[ale] IPv6 local devices with a prefix that may change

[Alex Carver]

Again, not everything is an OS and not everything is capable of being 
automated. The question comes down to solving the problem fully 
generically for all devices. Therefore it should work for an OS-free 
industrial controller as well as for a Dell or a Mac.

No, there's no mandate for IPv6, again this is entirely an academic 
question not based on anything specifically happening. It's just a 
matter of trying to think ahead, what if a device can't do IPv4 or 
somehow needs IPv6 to function (not likely now, perhaps it happens in 
the future). On the other than there are going to be plenty of devices 
that I have that are IPv4 only and I have no plans to retire them unless 
they fail.


On 2022-11-06 12:01, DJPfulio--- via Ale wrote:
> On 11/6/22 13:57, Alex Carver via Ale wrote:
>> So that's part of the problem, right?
>>
>> Let's say the prefix changes, how do I now access devices that are
>> using the old prefix? If I have 50 devices then I have to manually
>> change them all every time the prefix changes plus change everywhere
>> I use that IP.
>>
>> With IPv4/NAT I didn't have to worry, they were always the same IP no
>> matter what happened outside.
> 
> Stop using IP addresses, that's why we have DNS.  DNSmasq is a 
> light-enough DNS server for a LAN.  If you choose to run BIND, be 
> certain to read all the best practices and assume it will be hacked. The 
> master BIND server doesn't need to run all the time and really shouldn't 
> be handling client queries.
> 
> You don't have to manually change them all-the-time.  It isn't like 
> devices  change LANs all the time. Check out 'ansible' or 'expect' to 
> automate stuff.  Heck, if you don't like DNS, one of the first things I 
> did with Ansible was to automate pushing updated /etc/hosts files to 
> systems on the LAN. It is a fairly trivial thing to learn ansible and 
> templates.
> 
> You can keep using IPv4 on the LAN too. Is there some mandate for IPv6?
> 
> Or are you not disclosing something important about these systems - like 
> you move every week to a new conference and want to setup a LAN there?  
> That's a vastly different problem then worrying about a small business 
> or home LAN setup that changes once every 3-20 yrs.
> 
> Back before we had NAT, we'd get a subnet for every device and when we 
> changed providers, we'd spend a Friday night re-IPing all the systems.  
> I handled all the Unix systems.  It was "four easy commands" and all the 
> systems were modified - Linux, AIX, HP-UX, Solaris, and BSD. We didn't 
> change our domain on the LAN. We didn't change hostnames.  Just IPs. 
> Heck, even tcp-wrappers support domain-based rules, which we used. Same 
> for NIS (this was before NIS+).
> 
>>
>> On 2022-11-06 10:51, DJPfulio--- via Ale wrote:
>>> On 11/6/22 13:39, Alex Carver via Ale wrote:
>>>>
>>>> The thing I was primarily asking about is how to be robust
>>>> against a prefix change in an IPv6 implementation similar to how
>>>> IPv4/NAT helps isolate me from my WAN's IP changing assuming that
>>>> I don't use NAT because nearly everyone screams about it if you
>>>> threaten to use it on an IPv6 system.
>>>
>>> Isn't this solved by DNS?  Leave the hostnames the same, regardless
>>> of the LAN. Just change the IP stuff in the DNS ... and on the
>>> host, of course.
>>>
>>> I've been burned by using centralized DHCP reservations, so only
>>> use them for devices that are portable or don't support a method to
>>> manually configure IPs ON-THE-DEVICE. 
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