N+1 backup uses one standby AC to provide backup services for multiple ACs on an AC + Fit AP network. When the network runs properly, an AP sets up a capwap link only with the active AC. When the active AC fails or the CAPWAP link becomes faulty, the standby AC replaces the active AC to manage APs. The standby AC establishes a CAPWAP link with the AP to provide services.
In public places where a large number of users exist in a large area, many APs are deployed and managed by multiple ACs to provide free-of-charge WLAN access services. It is common for some large enterprises have branches in different areas. These enterprises deploy ACs in each branch to manage APs, providing WLAN access and e-mail services. These services require only low network reliability and allow for temporary service interruption.
In some cases, the existing network cannot provide reliable network services. If an AC fails, services on the AC are interrupted. To improve network reliability, an additional AC is required to provide backup services. The network administrator expects to use an AC as a backup of all ACs to reduce costs.
In dual-link cold backup mode, each active AC has an independent standby AC. Unlike dual-link cold backup, N+1 backup uses a standby AC to provide backup services for multiple ACs, which reduces device purchase costs.