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How can I permanently disable autoconfiguration of IPv6 in Linux? When I try to manually delete an address from an interface with:

ip -6 addr del 2001:0db8:85a3:0000:0000:8a2e:0370:7334/64 dev eth1

It will reappear a few seconds later, I want it to be gone permanently, but without disabling IPv6 all together.

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2 Answers 2

net.ipv6.conf.all.accept_ra=0 above should not be done, as RAs are necessary for indication of on-link and off-link for the prefix (as per RFC5942), as well as automated configuration of a number of other parameters, such as MTU, Neighbor Discovery timeouts etc.

If you want to disable autoconfiguration, either set the autoconf sysctl off as above, or switch off the A (autoconfiguration bit) in the Prefix Information Option (PIO) in the RA.

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up vote 14 down vote accepted

Auto configuration can be disabled temporary for eth1 with:

sudo sysctl -w net.ipv6.conf.eth1.autoconf=0
sudo sysctl -w net.ipv6.conf.eth1.accept_ra=0

or for all interfaces with:

sudo sysctl -w net.ipv6.conf.all.autoconf=0
sudo sysctl -w net.ipv6.conf.all.accept_ra=0

Reenabling works by using 1 instead of 0 in the call.

Disabling it permanently can be done with an entry to /etc/sysctl.conf. On Debian Etch (probably on newer too), without setting the accept_ra, the system will autoconfigure using the Link local adress (fe80..)

As Gart mentioned below, automatic address configuration and router discovery will be disabled if the host itself is a router and accept_ra is not 2, i.e

net.ipv6.conf.<iface|all|default>.forwarding=1

and

net.ipv6.conf.<iface|all|default>.accept_ra=0 or net.ipv6.conf.<iface|all|default>.accept_ra=1.

where iface is your interface

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2  
Also, automatic address configuration and router discovery will be disabled if the host itself is a router, i.e net.ipv6.conf.all.forwarding=1 is set. –  Gart Sep 18 '11 at 13:25

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