Wide Area Network (WAN) federation joins two or more Consul datacenters. When you enable WAN federation in each server cluster and declare one of them the primary datacenter, Consul agents can communicate using WAN gossip to function as if they were a single datacenter. 

WAN federation in your service mesh enables service-to-service communication across cloud regions, key/value store replication, and advanced strategies for traffic management such as [service failover](/consul/docs/manage-traffic/failover). Refer to the [WAN federation documentation](/consul/docs/east-west/wan-federation#guidance) for more information.