The Router advertisement configuration provides you with four buttons for setting up the Neighbor Discovery Protocol (NDP) if the device is to operate as an IPv6 router:
Each button opens a table with the settings for the corresponding function:
- Interface options: Enable or disable the following interface features:
- Send router advertisements: Regulates the periodic transmission of router advertisements and the response to router solicitations.
- Managed address configuration flag: With this function enabled, clients receiving this router advertisement will configure their addresses with Stateful Autoconfiguration (DHCPv6). Clients then automatically retrieve other information, such as the DNS server.
- Other flag: If this function is active, a client will attempt to obtain additional information via DHCPv6, such as DNS server addresses.For each prefix, you can specify whether or not a client should form addresses by auto-configuration: Navigate to the Prefix list under Allow auto-configuration (SLAAC).
- Default router: Defines how the device advertises itself as the default gateway or router.The parameters have the following functions:
- "Automatic": As long as a WAN connection exists, the device sends a positive router lifetime in the router advertisement messages. The result is that a client uses this router as the default gateway.If there is no WAN connection, the router sets the router lifetime to "0". A client then stops using this router as the default gateway.
- "Always": The router lifetime is always positive—i. e. greater than "0"—irrespective of the WAN connection status.
- "Never": The router lifetime is always "0".
- Router priority: Defines the preference of this router. Clients enter this preference into their local routing tables.
- Prefix list: Set the prefix options for the interfaces that are being used. The following settings are possible:
- Prefix: Enter a prefix that is announced in the router advertisements, e. g. "2001:db8::/64". The prefix length must always be exactly "/64", otherwise it will be impossible for clients to generate their addresses by adding their interface identifiers (with a length of 64 bits). If a prefix delegated by the provider is to be propagated automatically, set "::/64" here and enter the name of the corresponding WAN interface as the parameter Receive prefix from.
- Subnet ID: Here you enter the subnet ID that is to be combined with the prefix delegated by the provider. If the provider assigns the prefix "2001:db8:a::/48", for example, and the subnet ID is "0001" (or "1" for short), then the router advertisement on this interface is given the prefix "2001:db8:a:0001::/64". The maximum subnet length with a 48-bit long delegated prefix is 16 bits (i.e. 65,536 subnets), with available subnet IDs ranging from "0000" to "FFFF". With a delegated prefix of "/56", the maximum subnet length is 8 bits (i.e. 256 subnets) with subnet IDs ranging from "00" to "FF". In general, the subnet ID "0" is used when the WAN IPv6 address is formed automatically. This is why subnet IDs for LANs start at "1". The default setting is '1'.
- Allow auto configuration (SLAAC): Specifies whether the prefix is to be used for a stateless address autoconfiguration (SLAAC). The default setting is "enabled".
- Receive prefix from: Defines the name of the interface used to receive a prefix via DHCPv6 prefix delegation or via a tunnel. This prefix can be used to derive and propagate a subnet for each interface.
- DNS options: Defines the DNS information in router advertisements according to RFC 6106. The following settings are possible:
- Interface name: Name of the interface on which the IPv6 DNS server announces information in router advertisements.
- Primary DNS: IPv6 address of the first IPv6 DNS server (recursive DNS server, RDNSS, according to RFC 6106) for this interface.
- Secondary DNS: IPv6 address of the secondary IPv6 DNS server for this interface.
- Import DNS search list from the internal DNS server: Indicates whether the DNS search list or the own domain for this logical network should be inserted from the internal DNS server, e.g., "internal". The own domain can be configured under . The default setting is "enabled".
- Import DNS search list from WAN: Specifies whether the DNS search list sent by the provider (e.g., provider-xy.de) is announced in this logical network. This feature is available only if the prefix list is connected to the corresponding WAN interface under Receive prefix from.
- Route options: Defines the route option in router advertisements according to RFC 4191 (Route Information Option). The following settings are possible:
- Interface name: Defines the name of the logical interface to be used for sending router advertisements with this route option.
- Prefix: Prefix of the route option, e.g. "2001:db8::/32".
- Route preference: Preferred route. Possible values are "high", "medium" (default) and "low".