Regarding the issue of “conflict with other records, unable to add” in domain name resolution:
1、Same host header, same route, conflict situation.
If adding or modifying a URL forwarding record, there will be a conflict if there are already A, AAAA, CNAME, URL forwarding, SRV, or NS record values present.
Note: NS records do not actually conflict with other types of records. When NS resolution is done, it means that the resolution for that host is delegated to another authoritative DNS, and other types of records set for that host in our system will not take effect.
MX and CNAME records do not actually conflict in DNS. However, if both are resolved simultaneously, there is a possibility that a recursive query may check the MX record under the CNAME.
2、Host header limitation situation.
A Record
• In the host record field, enter the subdomain (e.g., to add a record for www.123.com, just enter “www”; if you want to add a record for 123.com, leave the host record blank and the system will automatically fill in “@” in the input box).
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9, a-z, -, _, *, and @.
• Allows *.abc.
• Allows empty host “@”
• Allows wildcard records “*”.
CNAME Record
• In the host record field, enter the subdomain (e.g., to add a record for www.123.com, just enter “www”; if you want to add a record for 123.com, leave the host record blank and the system will automatically fill in “@” in the input box; note that @’s CNAME can affect MX records).
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9, a-z, -, _, *, and @.
• Allows *.abc.
• Allows empty host “@”.
• Allows wildcard records “*”.
MX Record
• In the host record field, enter the subdomain (usually, to configure xxx@123.com email, the host record is left blank; if the host record is filled with “mail”, the email address will be xxx@mail.123.com).
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9, a-z, -, _, *, and @.
• *.abc is not allowed.
• Allows empty host “@”.
• Allows wildcard records “*”.
NS Record
• In the host record field, enter the subdomain (e.g., to delegate the resolution of www.123.com to another DNS server, just enter “www”; the host record “@” cannot be used for NS records; delegated subdomains will not affect the resolution of other subdomains).
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9 and a-z.
• *.abc is not allowed.
• Empty host “@” is not allowed.
• Wildcard records “*” are not allowed.
• Must be at least 2 levels (including 2 levels).
AAAA Record
• In the host record field, enter the subdomain (e.g., to add a record for www.123.com, just enter “www”; if you want to add a record for 123.com, leave the host record blank and the system will automatically fill in “@” in the input box).
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9, a-z, -, _, *, and @.
• Allows *.abc.
• Allows empty host “@”.
• Allows wildcard records “*”.
SRV Record
• The format for the host record is: service name.protocol type (e.g., _example-server._tcp).
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9, a-z, -, _, *, and @.
• *.abc is not allowed.
• Empty host “@” is not allowed.
• Wildcard records “*” are not allowed.
• Must be at least 2 levels (including 2 levels).
CAA Record
• Total length must not exceed 100 characters; single-level length must not exceed 60 characters.
• The host must be converted to lowercase.
• Maximum of 10 levels.
• Each level cannot start or end with a dash (”-”).
• Empty host “@” cannot be used with other records.
• If “” is present, it is only allowed as one character or must be at the beginning; otherwise, it is invalid. For example, abcd..a/ab*a is invalid.
• Only allowed characters are 0-9, a-z, -, _, *, and @.
• Allows *.abc.
• Allows empty host “@”.
• Allows wildcard records “*”.
3、Record Value Restrictions
AAAA Record Value Rules
• Composed of 8 segments of 4 hexadecimal digits each.
• Three formats:
• 2000:0000:0000:0000:0001:2345:6789:abcd
• 2000:0:0:0:1:2345:6789:abcd (leading zero compression)
• 2000::1:2345:6789:abcd (double colons, only one “::” is allowed)
• Total length must not exceed 100 characters.
A Record Value Rules
• The record value should be an IP address of the server (must be an IPv4 address, e.g., 1.1.1.1).
• Total length must not exceed 100 characters.
CNAME Record Value Rules
• For CNAME resolution, the record value must be another domain name, not a URL (e.g., www.dns.com).
• Total length must not exceed 100 characters.
MX Record Value Rules
• For MX records, consult your email service provider for the domain name provided by them. Using an IP address may lead to issues with email delivery. It is recommended to first set an A record for mailmx.a.com and then create an MX record pointing to mailmx.a.com.
• Total length must not exceed 100 characters.
• MX priority rules: 1-55.
NS Record Value Rules
• NS records are used to specify which DNS server is responsible for resolving the domain name (the value of NS records is the DNS server).
• Total length must not exceed 100 characters.
TXT Record Value Rules
• TXT record values can include any text (length must not exceed 253 characters, and backslash characters “\” are not supported). It cannot be empty and is generally used for anti-spam settings for enterprise email.
• Total length must not exceed 240 characters.
URL Forwarding Record Value Rules
• Supports multiple levels of domains: http://a.www.a.com/
• Supports ports: http://www.a.com:80
• Supports secondary directories: http://www.a.com:80/shuchao/
• Supports HTTPS: https://www.a.com/
• Total length must not exceed 100 characters.
URL Forwarding Introduction
• Explicit URL Forwarding: http://b.com/ points to http://a.com/example/ (any directory); when entering http://b.com/ in the browser address bar and pressing Enter, the address in the browser’s address bar will change from http://b.com/ to the actual target address http://a.com/example/.
• Implicit URL Forwarding: http://b.com/ points to http://a.com/example/ (any directory); when entering http://b.com/ in the browser address bar and pressing Enter, the address in the browser’s address bar remains http://b.com/, but the actual content accessed is from http://a.com/xxx/.
CAA Record Value Rules
• CA certificate authority authorization check. The format is: flag tag value. Where flag values range from 0 to 128; tag values are issue, issuewild, or iodef; value is a string that does not contain |, ", \, <, >, or Chinese characters. For example: 0 issue www.dns.com
• Total length must not exceed 100 characters.
SRV Record Value Rules
• For example: 0 100 389 NS.contoso.com
• 0: Priority. If multiple SRV records have the same service, users will first try to connect to the record with the lowest priority.
• 100: Load balancing mechanism. If multiple SRV records have the same priority, users will first try to connect to the record with the higher weight.
• 389: The port used by the service.
• NS.contoso.com: The host providing the service.
• Record values are separated by spaces.
• The first four parts must be numeric, and the last part must be a valid hostname.
• Total length must not exceed 100 characters.
