Server System Variables at server startup. The server also has an  admin_address  system variable that enables administrative connections on a dedicated interface. See Section 5.1.12.1, “Connection Interfaces” . If  bind_address  is specified, its value must satisfy these requirements: •Prior to MySQL 8.0.13,  bind_address  accepts a single address value, which may specify a single non-wildcard IP address or host name, or one of the wildcard address formats that permit listening on multiple network interfaces ( * ,  0.0.0.0 , or  :: ). •As of MySQL 8.0.13,  bind_address  accepts either a single value as just described, or a list of comma-separated values. When the variable names a list of multiple values, each value must specify a single non-wildcard IP address (either IPv4 or IPv6) or a host name. Wildcard address formats ( * , 0.0.0.0 , or  :: ) are not allowed in a list of values. •As of MySQL 8.0.22, addresses may include a network namespace specifier. IP addresses can be specified as IPv4 or IPv6 addresses. For any value that is a host name, the server resolves the name to an IP address and binds to that address. If a host name resolves to multiple IP addresses, the server uses the first IPv4 address if there are any, or the first IPv6 address otherwise. The server treats different types of addresses as follows: •If the address is  * , the server accepts TCP/IP connections on all server host IPv4 interfaces, and, if the server host supports IPv6, on all IPv6 interfaces. Use this address to permit both IPv4 and IPv6 connections on all server interfaces. This value is the default. If the variable specifies a list of multiple values, this value is not permitted. •If the address is  0.0.0.0 , the server accepts TCP/IP connections on all server host IPv4 interfaces. If the variable specifies a list of multiple values, this value is not permitted. •If the address is  :: , the server accepts TCP/IP connections on all server host IPv4 and IPv6 interfaces. If the variable specifies a list of multiple values, this value is not permitted. •If the address is an IPv4-mapped address, the server accepts TCP/IP connections for that address, in either IPv4 or IPv6 format. For example, if the server is bound to  ::ffff:127.0.0.1 , clients can connect using  --host=127.0.0.1  or  --host=::ffff:127.0.0.1 . •If the address is a “regular”  IPv4 or IPv6 address (such as  127.0.0.1  or  ::1 ), the server accepts TCP/IP connections only for that IPv4 or IPv6 address. •A network namespace can be specified for an IP address or a host name. •A network namespace cannot be specified for a wildcard IP address. •For a given address, the network namespace is optional. If given, it must be specified as a  / ns  suffix immediately following the address. •An address with no  / ns  suffix uses the host system global namespace. The global namespace is therefore the default. •An address with a  / ns  suffix uses the namespace named  ns . These rules apply to specifying a network namespace for an address: •The host system must support network namespaces and each named namespace must previously have been set up. Naming a nonexistent namespace produces an error. 773