Discovering cached content across multiple public IP addresses
If your network uses multiple public IP addresses to connect to the Internet, such that a content cache might register using a different address than a client uses for discovery, you need to provide both the content cache and the clients with a list of those addresses. Apple uses these lists to cross-match registration and discovery requests involving multiple public IP addresses.
To avoid manual configuration of clients, content caching uses DNS TXT records to publish the public IP address information for clients on your network. The TXT record needs to be published in the default DNS search domain used by your clients.
The correct data for the TXT record can be generated automatically or manually. In either case, you need to edit the DNS record, or give the settings to your DNS provider to create or edit the TXT record in the zone file.
Note: These records are necessary only for your internal network. External DNS doesn’t require the additional record.
To create the TXT records manually, see Enable content cache discovery across multiple public IP addresses in the macOS User Guide.
The following figure illustrates a network with two subnets sharing a single content cache: