Re: [gentoo-user] Local mail server

[Grant Taylor]

On 7/30/20 3:05 AM, antlists wrote:
> From what little I understand, IPv6 *enforces* CIDR.

Are you talking about the lack of defined classes of network; A, B, C, 
D, E?  Or are you talking about hierarchical routing?

There is no concept of a class of network in IPv6.

Hierarchical routing is a laudable goal, but it failed 15-20 years ago.

> Each customer is then given one of these 64-bit address spaces for their
> local network. So routing tables suddenly become extremely simple -
> eactly the way IPv4 was intended to be.

Except that things didn't work out that way.

Provider Independent addresses, multi-homing, and redundant routes mean 
that hierarchical routing failed 15-20 years ago.

Many providers try to address things so that hierarchical routing is a 
thing within their network.  But the reality of inter-networking between 
providers means that things aren't as neat and tidy as this on the Internet.

> This may then mean that dynDNS is part of (needs to be) the IPv6 spec,
> because every time a client roams between networks, its IPv6 address HAS
> to change.

Nope.

It's entirely possible to have clients roam between IPv6 (and IPv4) 
networks without (one of) it's address(es) changing.  Mobile IP.  VPNs. 
Tunnels.  BGP....

Sure, the connection to the network changes as it moves from network to 
network.  But this doesn't mean that the actual IP address that's used 
by the system to communicate with the world changes.

Take a look at IPv6 Provider Delegation.  At least as Comcast does it, 
means that you only have a link-local IPv6 address on the outside and a 
/56 on the inside of a network.  The world sees the globally routed IPv6 
network on the inside and doesn't give 2¢ what the outside link-net IPv6 
address is.  Comcast routes the /56 they delegate to you via the 
non-globally-routed IPv6 link-net IPv6 address.

There are multiple ways to keep the same IP while changing the 
connecting link.



-- 
Grant. . . .
unix || die