This feature requires Consul Enterprise with the Global Visibility, Routing, and Scale module.
Consul Network Segments enables operators to create separate LAN gossip segments in one Consul cluster. Agents in a segment are only able to join and communicate with other agents in it's network segment. This functionality is useful for clusters that have multiple tenants that should not be able to communicate with each other.
To get started with network segments you can review the tutorial on HashiCorp Learn for Network Segments.
Note: Prior to Consul 1.7.3, a Consul agent configured with too many network segments may not be able to start due to limitations in Serf.
»Consul Networking Models
To help set context for this feature, it is useful to understand the various Consul networking models and their capabilities.
Cluster: A set of Consul servers forming a Raft quorum along with a collection of Consul clients, all set to the same datacenter, and joined together to form what we will call a "local cluster". Consul clients discover the Consul servers in their local cluster through the gossip mechanism and make RPC requests to them. LAN Gossip (OSS) is an open intra-cluster networking model, and Network Segments (Enterprise) creates multiple segments within one cluster.
Federated Cluster: A cluster of clusters with a Consul server group per cluster each set per "datacenter". These Consul servers are federated together over the WAN. Consul clients make use of resources in federated clusters by forwarding RPCs through the Consul servers in their local cluster, but they never interact with remote Consul servers directly. There are currently two inter-cluster network models which can be viewed on HashiCorp Learn: WAN gossip (OSS) and Network Areas (Enterprise).
LAN Gossip Pool: A set of Consul agents that have full mesh connectivity among themselves, and use Serf to maintain a shared view of the members of the pool for different purposes, like finding a Consul server in a local cluster, or finding servers in a remote cluster. A segmented LAN Gossip Pool limits a group of agents to only connect with the agents in its segment.