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• group_replication_local_address 

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The value of this system variable can be changed while Group Replication is running, but the change only takes effect after you stop and restart Group Replication on the group member. 

group_replication_local_address  sets the network address which the member provides for connections from other members, specified as a host:port  formatted string. This address must be reachable by all members of the group because it is used by the group communication engine for Group Replication (XCom, a Paxos variant) for TCP communication between remote XCom instances. Communication with the local instance is over an input channel using shared memory. 

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## Warning 

Do not use this address for communication with the member. This is not the MySQL server SQL protocol host and port. 

The address or host name that you specify in group_replication_local_address  is used by Group Replication as the unique identifier for a group member within the replication group. You can use the same port for all members of a replication group as long as the host names or IP addresses are all different, and you can use the same host name or IP address for all members as long as the ports are all different. The recommended port for group_replication_local_address  is 33061. Note that the value you specify for this variable is not validated until the START GROUP_REPLICATION  statement is issued and the Group Communication System (GCS) is available. 

The network address configured by group_replication_local_address  must be resolvable by all group members. For example, if each server instance is on a different machine with a fixed network address, you could use the IP address of the machine, such as 10.0.0.1. If you use a host name, you must use a fully qualified name, and ensure it is resolvable through DNS, correctly configured /etc/ hosts  files, or other name resolution processes. From MySQL 8.0.14, IPv6 addresses (or host names that resolve to them) can be used as well as IPv4 addresses. An IPv6 address must be specified in square brackets in order to distinguish the port number, for example: 

group_replication_local_address= "[2001:db8:85a3:8d3:1319:8a2e:370:7348]:33061" 

If a host name specified as the Group Replication local address for a server instance resolves to both an IPv4 and an IPv6 address, the IPv4 address is always used for Group Replication connections. For more information on Group Replication support for IPv6 networks and on replication groups with a mix of members using IPv4 and members using IPv6, see Section 18.5.5, “Support For IPv6 And For Mixed IPv6 And IPv4 Groups” . 

For the purpose of IP address permissions for Group Replication, the address that you specify for each group member in group_replication_local_address  must be added to the list for the group_replication_ip_allowlist  (from MySQL 8.0.22) or group_replication_ip_whitelist  system variable on the other servers in the replication group. If any of the seed members for the group are listed in the group_replication_group_seeds  option 

