OpenWrt native IPv6-stack

This page applies to Barrier Breaker, Attitude Adjustment release 12.09.1 and later OpenWrt versions only. It is not valid for Backfire 10.03 or Attitude Adjustment 12.09. See Old IPv6 HowTo for these versions.

Obtaining IPv6 support

Barrier Breaker and later

  • Native IPv6-support with DHCPv6, an RA & DHCPv6-Server and an IPv6-firewall are installed and configured by default.
  • Transitioning technologies like 6in4, 6rd, 6to4 or ds-lite can be installed using the packages with the same names.
  • For WebUI-support install the package luci-proto-ipv6.

Implementation

Features

  • Prefix Handling
    • Management of prefixes, addresses and routes from upstream connections and local ULA-prefixes
    • Management of prefix unreachable-routes, prefix deprecation (RFC 6204) and prefix classes
    • Distribution of prefixes onto downstream interfaces (including size, ID and class hints)
    • Source-based policy routing to correctly handle multiple uplink interfaces, ingress policy filtering (RFC 6204)
  • Native IPv6 configuration
    • Automatic bootstrap from SLAAC, stateless DHCPv6, stateful DHCPv6, DHCPv6-PD and any combination
    • Handling of preferred and valid address and prefix lifetimes
    • Duplicate address and Link-MTU detection
    • DHCPv6 Extensions: Reconfigure, Information-Refresh, SOL_MAX_RT=3600
    • DHCPv6 Extensions: RDNSS, DNS Search Domain, NTP, SIP, ds-lite, prefix exclusion (experimental)
  • IPv6 transitioning technologies
    • Setup and management of IPv6-in-IPv4 tunnels (6rd, 6to4, 6in4)
    • Setup and management of IPv4-in-IPv6 tunnels (ds-lite)
    • Support for 6rd setup from DHCP and ds-lite setup from DHCPv6 (experimental)
  • Downstream IPv6 configuration
    • Server support for Router Advertisement, DHCPv6 (stateless and stateful) and DHCPv6-PD
    • Automatic detection of announced prefixes, delegated prefixes, default routes and MTU
    • Change detection for prefixes and routes triggering resending of RAs and DHCPv6-Reconfigure
    • Detection of client hostnames and export as augmented hosts-file
    • Support for RA & DHCPv6-relaying and NDP-proxying to e.g. support uplinks without prefix delegation

Compliance

Our aim is to follow RFC 7084 where possible. Nevertheless compliance has not been verified yet. Please notify us if you find any standard violations.

The following requirements of RFC 67084 are currently known not to be met.

  • RFC 7084 W-6 (SHOULD-requirement): There is no PCP-Client currently integrated in the stack.
  • RFC 7084 WAA-5 (SHOULD-requirement): The NTP-Server is requested and received but currently not processed or used.

Upstream configuration for WAN-Interfaces

The following sections describe the configuration of IPv6 connections to your ISP or an upstream router. Please note that most tunneling mechanisms like 6in4, 6rd and 6to4 may not work behind a NAT-router.

Native IPv6 connection

For an uplink with native IPv6-connectivity you can use the following example configuration. It will work both for uplinks supporting DHCPv6 with Prefix Delegation and those that don't support DHCPv6-PD or DHCPv6 at all (SLAAC-only).

/etc/config/network

config interface wan
        option ipv6 1 # only required for PPP-based protocols
        ...

config interface wan6
        option ifname   @wan
        option proto    dhcpv6

config interface lan
        option proto    static
        option ip6assign 60
        ...

:!: The package odhcp6c must be installed to use dhcpv6. See protocol.dhcpv6 for advanced configuration options.

Static IPv6 connection

Static configuration of the IPv6 uplink is supported as well. The following example demonstrates this.

/etc/config/network

config interface wan
        option ifname   eth1
        option proto    static
        option ip6addr  2001:db80::2/64   # Own address
        option ip6gw    2001:db80::1      # Gateway address
        option ip6prefix 2001:db80:1::/48 # Prefix addresses for distribution to downstream interfaces
        option dns      2001:db80::1      # DNS server

config interface lan
        option proto    static
        option ip6assign 60
        ...
For advanced configuration options see protocol.static

6in4 tunnel (HEnet tunnelbroker, sixxs static tunnel, ...)

6in4 tunnels are usually provided by external tunnel providers like HE.net or Sixxs. You can use the following example configuration as a basis.

/etc/config/network:

config 'interface' 'wan6'
        option 'proto' '6in4'
        option 'mtu' '1424'                          # the IPv6 tunnel MTU (optional)
        option 'peeraddr' '62.12.34.56'              # the IPv4 tunnel endpoint
        option 'ip6addr' '2001:DB8:2222:EFGH::2/64'  # the IPv6 tunnel 
        option 'ip6prefix' '2001:DB8:1234:ABCD::/64' # Your routed prefix (required!)
        # configuration options below are only valid for HEnet tunnels. ignore them for other tunnel providers.
        option tunnelid '123456' # HE.net tunnel id
        option username 'username' # HE.net username, which you use to login into tunnelbroker, not the User ID shows after you have login in.
        option password 'password' # HE.net password if there is no updatekey for tunnel
        option updatekey 'updatekey' # HE.net updatekey instead of password, default for new tunnels

config 'interface' 'lan'
        option 'proto' 'static'
        option ip6assign 60
...

:!: If you choose a name for your tunnel-interface that is different from 'wan6' make sure to add that name to the network-option of the firewall-zone 'wan' in /etc/config/firewall.

:!: The package 6in4 must be installed to use 6in4-tunnels. See protocol.6in4.ipv6-in-ipv4.tunnel for advanved configuration options.

:!: Note that HE.net assigns an "updatekey" by default for new tunnels since February 2014. If updatekey exists (visible in tunnel's advanced info page at the he.net site), it needs to be used instead of the password. Support for that option has been introduced in Openwrt trunk by r39646. Old tunnels without updatekey will continue to work with password.

6rd tunnel (ISP-provided IPv6 transition)

6rd is a tunnelmechanism based on 6to4. Unlike other tunneling mechanisms 6rd is usually provided by the ISP itself. Therefore you need to obtain the correct values for peeraddr, ip6prefix, ip6prefixlen and ip4prefixlen from your ISP.

/etc/config/network:

config 'interface' 'wan6'
        option 'proto' '6rd'
        option peeraddr '192.0.2.1' # The 6rd IPv4-gateway
        option ip6prefix '2123::'   # Your ISP's IPv6-prefix
        option ip6prefixlen '16'    # Your ISP's IPv6-prefix length
        option ip4prefixlen '0'     # Your ISP's IPv4 prefix mask

config 'interface' 'lan'
        option 'proto' 'static'
        option ip6assign 60
...

:!: If you choose a name for your tunnel-interface that is different from 'wan6' make sure to add that name to the network-option of the firewall-zone 'wan' in /etc/config/firewall.

:!: The package 6rd must be installed to use 6rd-tunnels. See protocol.6rd.ipv6.rapid.deployment for advanved configuration options.

6to4 tunnel

6to4 is the simplest IPv6 tunneling mechanism and relies on publicly available gateways.

/etc/config/network:

config 'interface' 'wan6'
        option 'proto' '6to4'

config 'interface' 'lan'
        option 'proto' 'static'
        option ip6assign 60
...

:!: If you choose a name for your tunnel-interface that is different from 'wan6' make sure to add that name to the network-option of the firewall-zone 'wan' in /etc/config/firewall.

:!: The package 6to4 must be installed to use 6to4-tunnels. See protocol.6to4.ipv6-in-ipv4.tunnel for advanved configuration options.

Dual-Stack Lite tunnel (ds-lite IPv4 in IPv6)

ds-lite is a transitioning-mechanism which is used by ISPs to support legacy IPv4-connectivity over a native IPv6 connection.

:!: ds-lite operation requires that IPv4 NAT is disabled. You should adjust your settings in /etc/config/firewall accordingly.

/etc/config/network:

config 'interface' 'wan6'
        option 'ifname' 'eth1'
        option 'proto' 'dhcpv6'

config 'interface' 'wan'
        option 'proto' 'dslite'
        option 'peeraddr' '2001:db80::1' # Your ISP's DS-Lite AFTR

:!: If you choose a name for your tunnel-interface that is different from 'wan' make sure to add that name to the network-option of the firewall-zone 'wan' in /etc/config/firewall.

:!: The package ds-lite must be installed to use ds-lite-tunnels. See protocol.dslite.dual-stack.lite for advanved configuration options.

Downstream configuration for LAN-Interfaces

OpenWrt includes a flexible local prefix delegation mechanism. It can be tuned for each downstream-interface individually with 3 parameters which are all optional:

  • ip6assign: Prefix size used for assigned prefix to the interface (e.g. 64 will assign /64-prefixes)
  • ip6hint: Subprefix ID to be used if available (e.g. 1234 with an ip6assign of 64 will assign prefixes of the form …:1234::/64)
  • ip6class: Filter for prefix classes to accept on this interface (e.g. wan6 will only assign prefixes with class "wan6" but not e.g. "local")

ip6assign and / or ip6hint-settings might be ignored if the desired subprefix cannot be assigned. In this case OpenWrt will first try to assign a prefix with the same length but different subprefix-ID. If this fails as well the prefix length is reduced until the assignment can be satisfied. If ip6hint is not set an arbitrary ID will be chosen. Setting the ip6assign-parameter to a value < 64 will allow the DHCPv6-server to hand out all but the first /64 via DHCPv6-Prefix Delegation to downstream routers on the interface. If the ip6hint is not suitable for the given ip6assign it will be rounded down to the nearest possible value.

If ip6class is not set then all prefix classes are accepted on this interface. The default class for a prefix is the interface-name (e.g. "wan6") or "local" for the ULA-prefix. This can be used to select upstream interfaces from which subprefixes are assigned. For prefixes received from dynamic-configuration methods like DHCPv6 it is possible that the prefix-class is not equal to the source-interface but e.g. augmented with an ISP-provided numeric prefix class-value.

Example (/etc/config/network):

config globals globals
        option ula_prefix fd00:db80::/48

config interface wan6
        option proto static
        option ip6prefix 2001:db80::/56
        ...

config interface lan
        option proto static
        option ip6assign 60
        option ip6hint 10
        ...

config interface guest
        option proto static
        option ip6assign 64
        option ip6hint abcd
        list ip6class wan6
        ...

The results of that configuration would be:

  • The lan interface will be assigned the prefixes 2001:db80:0:10::/60 and fd00:db80:0:10::/60.
  • The DHCPv6-server can offer both prefixes except 2001:db80:0:10::/64 and fd00:db80:0:10::/64 to downstream routers on lan via DHCPv6-PD.
  • The guest interface will only get assinged the prefix 2001:db80:0:abcd::/64 due to the class filter.

Router Advertisement & DHCPv6

OpenWrt features a versatile RA & DHCPv6 server and relay. Per default SLAAC, stateless and stateful DHCPv6 are enabled on an interface. If there are prefix of size /64 or greater present then addresses will be handed out from each prefix. If all prefixes on an interface have a size greater /64 then DHCPv6-Prefix Delegation is enabled for downstream-routers. If a default route is present the router advertises itself as default router on the interface.

OpenWrt is also able to detect when there is no prefix available from an upstream interface and can switch into relaying mode automatically to extend the upstream interface configuration onto its downstream interfaces. This is useful for putting an OpenWrt behind another IPv6-router which doesn't offer prefixes via DHCPv6-PD.

Example configuration section for server mode (/etc/config/dhcp)

config dhcp lan
    option dhcpv6 server
    option ra server

Example configuration section for relaying (/etc/config/dhcp)

config dhcp wan6
    option dhcpv6 relay
    option ra relay
    option ndp relay
    option master 1

config dhcp lan
    option dhcpv6 relay
    option ra relay
    option ndp relay

:!: The package odhcpd must be installed to provide these services.

Routing Mangement

OpenWrt uses a source-address and source-interface based policy-routing system. This is required to correctly handle different uplink interfaces. Each delegated prefix is added with an unreachable route to avoid IPv6-routing loops.

To determine the current status of routes you can consult the information provided by ifstatus.

Example (ifstatus wan6):

...
        "ipv6-address": [
                {
                        "address": "2001:db80::a00:27ff:fe67:cd9c",
                        "mask": 64,
                        "preferred": 1681,
                        "valid": 7081
                }
        ],
        "ipv6-prefix": [
                {
                        "address": "2001:db80:0:100::",
                        "mask": 56,
                        "preferred": 86282,
                        "valid": 86282,
                        "class": "wan6",
                        "assigned": {
                                "lan": {
                                        "address": "2001:db80:0:110::",
                                        "mask": 60
                                }
                        }
                }
        ],
        "route": [
                {
                        "target": "2001:db80::",
                        "mask": 48,
                        "nexthop": "fe80::800:27ff:fe00:0",
                        "metric": 1024,
                        "valid": 7081
                },
                {
                        "target": "::",
                        "mask": 0,
                        "nexthop": "fe80::800:27ff:fe00:0",
                        "metric": 1024,
                        "valid": 7081
                }
        ],
...
Interpretation:

  • On the interface 2 routes are provided: 2001:db80::/48 and a default-route via the router fe80::800:27ff:fe00:0.
  • These routes can only be used by locally generated traffic and traffic with a suitable source-address, that is either one of the local addresses or an address out of the delegated prefix.

:!: OpenWrt adds IPv6-routes (like default routes) to specific routing-tables and not the main-table thus they may not be seen by default. You can use the command ip -6 rule to list all current routing policies.

Migration from Attitude Adjustment 12.09 and earlier

IPv6 Forwarding

To ensure that IPv6 forwarding is working correctly, please check that your /etc/sysctl.conf contains the following entries:

net.ipv6.conf.default.forwarding=1
net.ipv6.conf.all.forwarding=1

Downstream configuration for LAN-Interfaces

It is discouraged to use ip6addr to set addresses / prefixes on downstream interfaces (e.g. lan) because it can easily lead to conflicts with the local address delegation. Also it might lead to unexpected result or brokenness due to the source-based policy-routing used in the IPv6-stack. Please use the new options ip6assign and ip6hint instead.

Example: If your delegated prefix is 2001:db80:1234::/48 and you want your lan interface to have the subprefix 2001:db80:1234:5678::/64 you could use the following configuration:

config 'interface' 'lan'
       option 'proto' 'static'
       option 'ip6assign' '64'
       option 'ip6hint' '5678'
       ...

Router Advertisement & DHCPv6

The use of radvd is now unnecessary. The service 6relayd is used for Router Advertisement and DHCPv6 and picks up addresses from interfaces automatically. To configure the 6relayd service see 6relayd.

Upstream Configuration for WAN-Interfaces

Generic Changes

Router Advertisements are not accepted by default anymore and thus OpenWrt will not configure itself with default routes and / or addresses. Also the interface-options accept_ra and send_rs have been removed. You should add an interface with proto dhcpv6 - also for receiving RAs only - as described in Native IPv6 Connection.

6in4 tunnel and Static IPv6 connection

It is now necessary to add your routed-prefix (e.g. routed /48 of your tunnel) as option ip6prefix to the tunnel/static-interface in /etc/config/network. If you omit this option your lan-clients will not be able to reach the internet.

Example:

config 'interface' 'wan6'
        option 'proto' '6in4'
        option 'peeraddr' '62.12.34.56
        option 'ip6addr' '2001:DB8:2222:EFGH::2/64'
        option 'ip6prefix' '2001:DB8:1234:ABCD::/64' # <- Your routed prefix
        ...

6rd and 6to4 tunnel

Your public address prefix is now automatically calculated and sent to the network subsystem (netifd). You should follow the advice for lan-interface configuration.

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doc/uci/network6.txt · Last modified: 2014/07/18 05:47 by ayaka