H3C Technologies H3C S12500-X Series Switches - Manual (Page 91)

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In addition, you can configure a DNS suffix that the system automatically adds to the provided domain
name for resolution. A DNS suffix manually configured takes precedence over the one dynamically
obtained through DHCP, and a DNS suffix configured earlier takes precedence. The DNS resolver first
uses the suffix that has the highest priority. If the name resolution fails, the DNS resolver uses the suffix that
has the second highest priority, and thus in turn.
Configuration guidelines
Follow these guidelines when you configure dynamic domain name resolution:
• You can specify DNS server IPv4 addresses for the public network and up to 1024 VPNs, and
specify a maximum of six DNS server IPv4 addresses for the public network or each VPN.
• You can specify DNS server IPv6 addresses for the public network and up to 1024 VPNs, and
specify a maximum of six DNS server IPv6 addresses for the public network or each VPN.
• An IPv6 name query is first sent to the IPv6 DNS servers. If no reply is received, it is sent to the IPv4
DNS servers.
• You can specify domain name suffixes for the public network and up to 1024 VPNs, and specify
a maximum of 16 domain name suffixes for the public network or each VPN.
Configuration procedure
To configure dynamic domain name resolution:
Step Command Remarks
1. Enter system view. system-view N/A
2. Specify a DNS server IP
address.
• Specify a DNS server IPv4 address:
dns server ip-address [ vpn-instance
vpn-instance-name ]
• Specify a DNS server IPv6 address:
ipv6 dns server ipv6-address
[ interface-type interface-number ]
[ vpn-instance vpn-instance-name ]
Use at least one command.
By default, no DNS server IP
address is specified.
3. (Optional.) Configure a
DNS suffix. dns domain domain-name
[ vpn-instance vpn-instance-name ]
By default, no DNS suffix is
configured. Only the provided
domain name is resolved.
Specifying the source interface for DNS packets
By default, the device uses the primary IP address of the output interface of the matching route as the
source IP address of a DNS request. Therefore, the source IP address of the DNS packets might vary with
DNS servers. In some scenarios, the DNS server only responds to DNS requests sourced from a specific
IP address. In such cases, you must specify the source interface for the DNS packets so that the device
can always uses the primary IP address of the specified source interface as the source IP address of DNS
packets.
When sending IPv4 DNS request, the device uses the primary IPv4 address of the source interface as the
source IP address of the DNS request. When sending IPv6 DNS request, the device selects an IPv6
address from the addresses configured on the source interface as defined in RFC 3484 as the source IP
address of the DNS request.