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Kernel removes ::1 but not 127.0.0.1 when setting lo down:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever

# ip link set lo down

1: lo: <LOOPBACK> mtu 65536 qdisc noqueue state DOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo

Expected results:

As loopback addresses are automatically set up on activation of the loopback interface, I would expect both of them to be removed.

Actual results:

IPv6 loopback address is removed but IPv4 loopback address isn't.

Tested with:

kernel-3.7.4-204.fc18.x86_64
iproute-3.6.0-5.fc18.x86_64

This is not only for lo. All devices behave like this

I was also surprised by learning that statically assigned IPv6 addresses are removed on 'ip link set .... down' which probably shouldn't be (IPv4 addresses have never been removed).

(In reply to comment #2)
> This is not only for lo. All devices behave like this

Adding information after IRC talk:

For IPv4, only loopback address is an automatically assigned address by kernel. Therefore behavior regarding the loopback address is not comparable to the addresses assigned by userspace software.

I personally think, that kernel should automatically remove all (and only) addresses that it configured, when the interface is set down and that there shouldn't be any difference between IPv4 and IPv6 addresses, as they are the same in all other aspects.

Although I agree with you, I do not believe this behaviour can be changed upstream. It would break apps/scripts which expect all ipv6 addresses are removed on down. Closing this as wontfix. Please feel free to reopen if something changes.