IPv6 Router Advertisement Options for DNS

Neighbor Discovery (ND) for IP version 6 and IPv6 stateless address autoconfiguration provide ways to configure either fixed or mobile nodes with one or more IPv6 addresses, default routers, and other parameters [RFC4861][RFC4862]. ExtremeXOS now supports two RA options that provide the DNS information needed for an IPv6 host to reach Internet services.

The Recursive DNS Server (RDNSS) option contains the addresses of recursive DNS servers, and the DNS Search List (DNSSL) option for the Domain Search List that maintains parity with the DHCPv6 options, and ensures the necessary functionality to determine the search domains.

The RDNSS option contains one or more IPv6 addresses of recursive DNS servers. All of the addresses share the same lifetime value. If you wish to have different lifetime values, you can use multiple RDNSS options.

The DNSSL option contains one or more domain names of DNS suffixes. All of the domain names share the same lifetime value. If you wish to have different lifetime values, you can use multiple DNSSL options.

The existing ND message (i.e., Router Advertisement) is used to carry this information. An IPv6 host can configure the IPv6 addresses of one or more RDNSSs through RA messages. Using the RDNSS and DNSSL options, along with the prefix information option based on the ND protocol, an IPv6 host can perform the network configuration of its IPv6 address and the DNS information simultaneously without needing DHCPv6 for the DNS configuration. The RA options for RDNSS and DNSSL can be used on any network that supports the use of ND.

For IPv6-only networks that rely only on IPv6 stateless Autoconfiguration as a deployment model, these two options allow a host to configure its DNS information. This is useful when there is no DHCPv6 infrastructure, or hosts do not have a DHCPv6 client. For networks where DHCPv6 is deployed, you might not need an RA-based DNS configuration.

You can configure the RA options for DNS using the following commands:

Default RDNSS Lifetime

configure {vlan} vlan_name> router-discovery {ipv6} rdnss-lifetime [<rdnss_lifetime> | infinity | auto]

Add RDNS Server with Optional RDNSS Lifetime

configure {vlan} vlan_name router-discovery {ipv6} add rdnss ipaddress {{rdnss-lifetime} [rdnss_lifetime | infinity]}

Default DNSSL Lifetime

configure {vlan} vlan_name router-discovery {ipv6} dnssl-lifetime [dnssl_lifetime | infinity | auto]

Add a DNS suffix to DNSSL

configure {vlan} vlan_name router-discovery {ipv6} add dnssl dns_suffix {{dnssl-lifetime} [dnssl_lifetime | infinity]}