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Re: I need to totally stop ANY indication of ipv6 connectivity, how.




Hi Gene,

[You asked how to do this so I am answering, but for the record I
don't believe it is a good idea to disable the current version of
the Internet protocol and rely on the legacy Internet protocol. If
there are problems with IPv6 then I think they should be fixed, not
disabled.]

On Sat, May 25, 2019 at 05:38:22AM -0400, Gene Heskett wrote:
> I have the following in /etc/sysctl.conf:
> 
> net.ipv6.conf.all.disable_ipv6 = 1
> net.ipv6.conf.default.disable_ipv6 = 1
> net.ipv6.conf.lo.disable_ipv6 = 1
> net.ipv6.conf.eth0.disable_ipv6 = 1
> net.ipv6.conf.eth1.disable_ipv6 = 1
> net.ipv6.conf.ppp0.disable_ipv6 = 1
> net.ipv6.conf.tun0.disable_ipv6 = 1

Note that there can be race conditions because some of these sysctls
may not exist until the network interfaces themselves exist and/or
are brought up. You may therefore prefer to disable IPv6 at the
kernel command line level, or by using post-up commands in each
interface stanza in /etc/network/interfaces.

Disable at kernel command line: ipv6.disable=1

Example of disabling in /etc/network/interfaces:

auto eth0
iface eth0 …
    address …
    netmask …
    gateway …
    post-up echo 1 > /proc/sys/net/ipv6/conf/$IFACE/disable_ipv6

(assuming you leave the entries for "all" and "default" in
/etc/sysctl.conf)

> but its not enough to stop this from ip a:
> : eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state 
> UP group default qlen 1000
>     link/ether 00:1f:c6:62:fc:bb brd ff:ff:ff:ff:ff:ff <--ipv6 crap.

This isn't "ipv6 crap". That is the MAC address of your Ethernet
interface at the link level. IPv6 address output from "ip a" start
with "inet6" not "link/ether". For example:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether aa:00:00:4b:a0:c1 brd ff:ff:ff:ff:ff:ff
    inet6 2001:ba8:1f1:f019::2/128 scope global 
       valid_lft forever preferred_lft forever

Possibly there isn't even any IPv6 addressing present and you are
experiencing some other problem so, as usual, I recommend focusing
on the details of the actual problem you have rather than trying to
guess what the cause is and only asking about that.

> Any ipv6 connectivity is at least 100 miles away.

Incorrect; IPv6 can be used on a local network, and on the loopback
interface of every host. As it is the current version of the
Internet protocol, it can and should be used any time any IP
networking wants to be used, even within the same host. If you want
to disable that and revert to legacy protocols that should be
recognised as a deviation from the norm.

> So I need a way to shut it off so thouroughly that nothing in a
> ./configure script believes its a working connection.

Almost certainly not your issue. Apps are supposed to support IPv6
but only use it if there is a global scope IPv6 address on the
interface that the app is trying to use. We don't even know if that
is what is happening because you haven't shown us the actual problem.

> Its creating all sorts of hate, discontent and general havoc
> trying to build a tarball because it makes things disable ipv4,
> the only WORKING connectivity my little 7 or 9 machine network,
> all behind dd-wrt anyway, has.

If it really is causing problems then show us those problems and I'm
sure they can be fixed, but you haven't demonstrated any, so it's
highly likely that this is a result of a misunderstanding.

> Please advise, we are still in jurrasic park here in WV.

Fortunately the Linux kernel and network stack is not.

Cheers,
Andy

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