Re: ipv6 ::1 and lo dev

On Wed, 18 Aug 2021 22:17:55 +0200
Willy Tarreau [off-list ref] wrote:

On Wed, Aug 18, 2021 at 07:47:37PM +0200, Thorsten Glaser wrote:

quoted

On Wed, 18 Aug 2021, Oleg wrote:
  

quoted

I try to replace ::1/128 ipv6 address on lo dev with ::1/112 to
access more than 1 address(like with ipv4 127.0.0.1/8). But i get  

AIUI this is not possible in IPv6, only :: and ::1 are reserved,
the rest of ::/96 is IPv4-compatible IPv6 addresses.

I never understood why you'd want more than one address for loopback
anyway (in my experience, the more addresses a host has, the more
confused it'll get about which ones to use for what).  

It's because you've probably never dealt with massive hosting :-)
Sometimes binding a full /24 (or smaller) on the loopback, be it
for listening addresses or to be used as sources to connect to
next hops, is extremely useful.

Willy

In the large scale routing world addresses are assigned to loopback
interface because it keeps routing protocols happy. If interface goes
down loopback stays around.