Connection Management As a result, the administrative interface supports encrypted connections using its own TLS context. When clients connect to the administrative interface, they should use certificate and key files specific to that interface. For example (enter the command on a single line): mysql --protocol=TCP --port=33062 --ssl-ca=admin-ca.pem --ssl-cert=admin-client-cert.pem --ssl-key=admin-client-key.pem 5.1.12.3 DNS Lookups and the Host Cache The MySQL server maintains an in-memory host cache that contains information about clients: IP address, host name, and error information. The Performance Schema  host_cache  table exposes the contents of the host cache so that it can be examined using  SELECT  statements. This may help you diagnose the causes of connection problems. See Section 27.12.21.2, “The host_cache Table” . The following sections discuss how the host cache works, as well as other topics such as how to configure and monitor the cache. •Host Cache Operation •Configuring the Host Cache •Monitoring the Host Cache •Flushing the Host Cache •Dealing with Blocked Hosts •By caching the results of IP-to-host name lookups, the server avoids doing a Domain Name System (DNS) lookup for each client connection. Instead, for a given host, it needs to perform a lookup only for the first connection from that host. •The cache contains information about errors that occur during the client connection process. Some errors are considered “blocking.”  If too many of these occur successively from a given host without a successful connection, the server blocks further connections from that host. The max_connect_errors  system variable determines the permitted number of successive errors before blocking occurs. Host Cache Operation The server uses the host cache only for non-localhost TCP connections. It does not use the cache for TCP connections established using a loopback interface address (for example,  127.0.0.1  or  ::1 ), or for connections established using a Unix socket file, named pipe, or shared memory. The server uses the host cache for several purposes: For each applicable new client connection, the server uses the client IP address to check whether the client host name is in the host cache. If so, the server refuses or continues to process the connection request depending on whether or not the host is blocked. If the host is not in the cache, the server attempts to resolve the host name. First, it resolves the IP address to a host name and resolves that host name back to an IP address. Then it compares the result to the original IP address to ensure that they are the same. The server stores information about the result of this operation in the host cache. If the cache is full, the least recently used entry is discarded. The server performs host name resolution using the  gethostbyaddr()  and  gethostbyname()  system calls. 987