The hostname set corresponding to a domain name is obtained by using the DNS server.

The DNS server supports IPv4 NAPTR record query, helping the client select an optimal node.

Figure 1 Querying for an NAPTR record


http://localhost:7904/pages/31185199/02/31185199/02/resources/figure/cn_10_01_1430016_fig1.png

• The DNS server finds the hostname list corresponding to a domain
  name based on the configuration and sends the hostname list to the DNS
  client.
• The DNS client reinitiates a query based on the query ID carried in the result until the corresponding IP address is obtained.
• The DNS client selects an optimal node based on the interface type, protocol type, and selection policy in the list.

This document is very well done

Does Huawei DNS Support IPv4 NAPTR Record Query?

useful document, thanks