Host labels let you group hostnames or subnets that share similar configuration needs. When you use hostnames in a host label, the appliance queries your DNS to find the corresponding IP addresses and uses those IPs to match destination traffic for any rules using the host label. Starting with RiOS 9.16.0, IPv6 support is included for host label subnets.

Appliances automatically resolve hostnames once every 24 hours to stay updated with any IP changes. If any resolution issues occur—either during this automatic process or during a manual resolution—the host labels page will show a summary alerting you to the problem. The good news: once an appliance resolves a new IP for a hostname, all rules using that host label are updated automatically; you don’t need to make manual changes.

You also have the option to manually resolve hostnames at any time, which resets the next automatic resolution to 24 hours later. Additionally, you can choose whether to show or hide the resolved IP addresses for each hostname.

Appliances include a predefined host label, SaaS Application, which detects any IP addresses that carry traffic destined to a cloud, or SaaS, service. As SaaS applications are added or deleted, the host label is automatically updated with the list of associated IP addresses. This host label removes the requirement that domain rules and SaaS acceleration be mutually exclusive. Use this label with an auto discover in-path rule, and set cloud acceleration to auto.