The radvd configuration is located in /etc/config/radvd. This configuration is responsible for defining interface settings, prefixes, routes and RDNSS announcements.

Below is an overview of the section types that may be defined in the radvd configuration. A minimal radvd configuration for a local network usually consists of at least one interface (lan) and one prefix section. Each section type may occur multiple times in the config but interface sections are limited to one section per interface.

Sections of type interface specify global, interface specific options for radvd. The default configuration defines one section for the lan interface:

config 'interface' option 'interface' 'lan' option 'AdvSendAdvert' '1' option 'AdvManagedFlag' '0' option 'AdvOtherConfigFlag' '0' option 'ignore' '1'

• lan is the logical interface name this section applies to
• AdvSendAdvert 1 enables router advertisements and solicitations
• AdvManagedFlag 0 disables the additional stateful administered autoconfiguration protocol (RFC2462)
• AdvOtherConfigFlag 0 disables the autoconfiguration of additional, non address information (RFC2462)
• ignore 1 disables any advertisements on this interface. It must be set to 0 or removed in order to enable radvd for this interface

Each interface requires a separate interface declaration (i.e. the interface option only accepts a single interface name).

Below is the listing of defined options for interface sections.

The prefix sections declare IPv6 subnets where client addresses are derived from. In the default config, one example prefix section is included with the following values:

config 'prefix' option 'interface' 'lan' option 'AdvOnLink' '1' option 'AdvAutonomous' '1' option 'AdvRouterAddr' '0' option 'ignore' '1'

• lan is the logical interface name this section applies to
• AdvOnLink 1 specifies that the announced prefix can be used for on-link determination (RFC4861)
• AdvAutonomous 1 indicates that the announced prefix can be used for autonomous address configuration (RFC4862)
• AdvRouterAddr 0 forced radvd to send the network prefix instead of the sending interface address
• ignore disables this prefix declaration

All defined options for the prefix section are listed below.

Sections of type route define arbritary IPv6 CIDR routes to advertise to clients. A minimal section may look like this:

config 'route' option 'interface' 'lan' option 'prefix' '2001:0DB8:1234:5678::/64' option 'AdvRouteLifetime' 'infinity'

• lan is the logical interface name this section applies to
• 2001:0DB8:1234:5678::/64 specifies the prefix to advertise
• AdvRouteLifetime infinity sets the route lifetime to forever

The defined options for route sections are:

Recursive DNS Server (rdnss) sections define DNS server advertisements as specified in RFC5006. A minimal rdnss section contains the interface and optionally an IPv6 address pointing to a recursive DNS resolver:

config 'rdnss' option 'interface' 'lan' list 'addr' '2001:DB8:1234:5678::1'

• lan is the logical interface name this section applies to
• 2001:DB8:1234:5678::1 specifies the DNS server used for resolving

The options below are defined for rdnss sections:

Name	Type	Required	Default	Description
interface	string	yes	(none)	Specifies the logical interface name this section belongs to
ignore	boolean	no	0	Ignore this DNS declaration
addr	list of IPv6 addresses	no	(link-local address of interface)	Specifies the advertised IPv6 DNS servers. Note that leaving this unspecified advertises the link-local address of the interface, which generally does not work for DNS clients, causing DNS timeouts and weirdness, so it is best to specify the global-scope IPv6 address of your interface here.
AdvRDNSSPreference	integer	no	8	Specifies the preference of the DNS server, compared to other DNS servers advertised and used. 0 to 7 means less important than manually configured nameservers in resolv.conf, while 12 to 15 means more important This feature was removed from the final RFC but can still be used for experimental purposes Recent radvd versions (1.7+) ignore this option
AdvRDNSSOpen	boolean	no	0	Indicates whether that RDNSS continues to be available to hosts even if they moved to a different subnet Recent radvd versions (1.7+) ignore this option
AdvRDNSSLifetime	integer/string	no	1200	Specifies the maximum duration how long the RDNSS entries are used for name resolution. A value of 0 means the nameserver should no longer be used. The special value infinity means forever

DNS search list (dnssl) sections provide domain search suffixes as defined in RFC6106. A minimal dnssl section contains the corresponding interface and at least one domain suffix:

config 'dnssl' option 'interface' 'lan' list 'suffix' 'company.local' list 'suffix' 'local'

• lan is the logical interface name this section applies to
• company.local and local specify the advertised domain suffixes

The options below are defined for dnssl sections:

It is possible to use a traditional radvd.conf file and bypass the autogeneration from UCI values by defining the following section in /etc/config/radvd:

config 'radvd' option 'config_file' '/etc/radvd.conf'

Simple example: advertising on two internal interfaces, wired and wifi, using the default configuration.

config interface
        option interface        wired

config prefix
        option interface        wired

config rdnss
        option interface        wired


config interface
        option interface        wifi

config prefix
        option interface        wifi

config rdnss
        option interface        wifi