Deploying Group Replication in Single-Primary Mode Alternatively you can use the same host name or IP address for all members as long as the ports are all different, for example as shown in Section 18.2.2, “Deploying Group Replication Locally” . The connection that an existing member offers to a joining member for Group Replication’s distributed recovery process is not the network address configured by  group_replication_local_address . Up to MySQL 8.0.20, group members offer their standard SQL client connection to joining members for distributed recovery, as specified by MySQL Server’s  hostname  and  port  system variables. From MySQL 8.0.21, group members may advertise an alternative list of distributed recovery endpoints as dedicated client connections for joining members. For more details, see Section 18.5.3.1, “Connections for Distributed Recovery” . Distributed recovery can fail if a joining member cannot correctly identify the other members using the host name as defined by MySQL Server’s  hostname system variable. It is recommended that operating systems running MySQL have a properly configured unique host name, either using DNS or local settings. The host name that the server is using for SQL client connections can be verified in the  Member_host  column of the Performance Schema table  replication_group_members . If multiple group members externalize a default host name set by the operating system, there is a chance of the joining member not resolving it to the correct member address and not being able to connect for distributed recovery. In this situation you can use MySQL Server’s  report_host  system variable to configure a unique host name to be externalized by each of the servers. The  hostname:port  listed in  group_replication_group_seeds is the seed member’s internal network address, configured by group_replication_local_address  and not the  hostname:port  used for SQL client connections, which is shown for example in the Performance Schema table  replication_group_members . The server that starts the group does not make use of this option, since it is the initial server and as such, it is in charge of bootstrapping the group. In other words, any existing data which is on the server bootstrapping the group is what is used as the data for the next joining member. The second server joining asks the one and only member in the group to join, any missing data on the second server is replicated from the donor data on the bootstrapping member, and then the group expands. The third •Configuring  group_replication_group_seeds  sets the hostname and port of the group members which are used by the new member to establish its connection to the group. These members are called the seed members. Once the connection is established, the group membership information is listed in the Performance Schema table  replication_group_members . Usually the  group_replication_group_seeds  list contains the  hostname:port  of each of the group member’s  group_replication_local_address , but this is not obligatory and a subset of the group members can be chosen as seeds. Important Important 3705