[fpc-other] Your thoughts on cloud based server instances?

[Santiago A.]

El 13/03/2017 a las 17:33, Luca Olivetti escribió:
> So, while for a client ipv6 is enough, for a server ipv4 is mandatory.
> Glad I'm still on ipv4 ;-) (since I host my own mail server).
>
> Bye
Well, that is not accurate.

IPV6 can connect only to IPV6
IPV4 can connect only to IPV4

In fact, if you have  active the two stacks in your computer (if you
have IPV6, odds you also have IPV4)  your network card has two IPs
address: an IPV6 address and an IPV4 address. And IPV6 address is not a
translation of the IPV4 address, both addresses are not related at all.

So, If you have a mail server and you want it IPV6 and IPV4 aware, it
must listen both IPs: IPV6 and IPV4.

Usually devices that have IPV6 have also IPV4 stack, but routing  from
IPV4 to IPV6 is something that most devices will not have to do. Only
routers in a networks that has both types of devices, probably only ISPs
or routers from large networks. There is a range of IPV6 reserved to old
IPV4: 0:0:0:0:0:FFFF:x.x.x.x. (also written ::FFFF.x.x.x.x)

i.e. if you have two ISPs with IPV6 and you send a message using IPV4.
from 1.1.1.1 to 2.2.2.2, you ISP will convert to from ::FFFF.1.1.1.1 to
::FFFF.2.2.2.2 (in IPV6 format::FFFF:0101:0101 and ::FFFF:0202:0202)
before sending to another ISP with IPV6, and then, the second ISP with
use IPV4 to send it to 2.2.2.2

The problem nowadays is that many intermediate devices (routers etc)
don't support IPV6. DNS servers are ready to support IPV6, but most DNS
don't have it configured.
So transition of ISPs to IPV6 is going to take long. You will be able to
live years with only IPV4. And probably we won't see in our life
only-IPV6 devices, let alone ISPs.

-- 
Saludos

Santiago A.
svaa at ciberpiula.net