Overview of IPv6 DNS
IPv6 DNS is a distributed database used in TCP and IP applications and completes resolution between IPv6 addresses and domain names.
Each host on the IPv6 network is identified by an IPv6 address. To access a host, a user must obtain the host IPv6 address first. It is difficult for users to remember IPv6 addresses of hosts. Therefore, host names in the format of strings are designed. In this way, users can use the simple and meaningful domain names instead of the complicated IPv6 addresses to access hosts by resolution of the DNS server on the network.
The device can function as an IPv6 DNS client and IPv6 DNS proxy or relay.
As shown in Figure 10-1, the RouterIndustrial Switch Router functions as an IPv6 DNS client and supports static and dynamic domain name resolution.
- Static domain name resolution: Mappings between domain names and IPv6 addresses are configured manually. To obtain the IPv6 address by resolving a domain name, the DNS client searches the static domain name resolution table for the specified domain name.
- Dynamic domain name resolution: Dynamic domain name resolution is implemented by a DNS server. The DNS server receives domain name resolution requests from DNS clients. The DNS server searches for the corresponding IPv6 address of the domain name in its DNS database. If no matching entry is found, it sends a query message to a higher-level DNS server. This process continues until the DNS server finds the corresponding IPv6 address or detects that the corresponding IPv6 address of the domain name does not exist. Then the DNS server returns a result to the DNS client.The RouterIndustrial Switch Router IPv6 domain name resolution system must support the following DNS query modes:
- AAAA query
- IPv6 PTR query.
- A6 query
Functioning as the DNS Proxy or Relay
As shown in Figure 10-2, an IPv6 DNS client on the LAN can connect to an external IPv6 DNS server through the RouterIndustrial Switch Router enabled with IPv6 DNS proxy or relay. After the external DNS server translates the domain name of the IPv6 DNS client to an IP address, the IPv6 DNS client can access the Internet.
IPv6 DNS relay is similar to IPv6 DNS proxy. The difference is that the IPv6 DNS proxy searches for DNS entries saved in the domain name cache after receiving DNS query messages from DNS clients. The IPv6 DNS relay, however, directly forwards DNS query messages to the DNS server, reducing the cache usage.