netipv6confallforwarding

Net.ipv6.conf.all is a Linux kernel sysctl setting that governs IPv6 behavior across all network interfaces. It is part of the sysctl interface exposed at /proc/sys/net/ipv6/conf/all. The parameters here apply to every IPv6-capable interface on the system, and can be supplemented or overridden by per-interface settings under net.ipv6.conf.[interface] or by net.ipv6.conf.default for interfaces created after boot.

Common tunables in this namespace control core IPv6 behavior. disable_ipv6, when set to 1, disables IPv6 on all interfaces. forward enables or disables IPv6 packet forwarding, which is relevant for systems acting as routers. hop_limit specifies the default Hop Limit used for outgoing IPv6 packets. accept_ra controls whether Router Advertisements are accepted on interfaces, influencing whether the host can act as a router. max_addresses sets the maximum number of IPv6 addresses that can be assigned to an interface. proxy_ndp enables or disables Proxy Neighbor Discovery Protocol, affecting how the host handles neighbor resolution for other addresses.

Configuration is typically done at runtime via the sysctl interface, for example: sysctl -w net.ipv6.conf.all.disable_ipv6=1. To persist changes across reboots, values can be placed in a file under /etc/sysctl.d/ or in /etc/sysctl.conf and applied with sysctl --system.

Notes and considerations: changes here can affect network connectivity and behavior of services, so they should be tested in a controlled environment. Root privileges are required to modify these settings. The all namespace interacts with the default and per-interface namespaces, so careful coordination is needed when configuring a system that also uses virtual interfaces or containers.