It's not just multiple AC devices that make up different backup modes.
AC backup type is based on your AC type, the version to develop the corresponding backup mode.
Different backup modes, his role is also different.
The following table can clearly tell you which types of AC can build which types of backup mode.
I hope I can help you.
The device supports hot-standby (HSB), dual-link cold backup, and N+1 backup modes.
| Backup Mode | Device Model and Version | Characteristics |
| HSB backup, available in two modes: 1.Dual-link HSB 2.VRRP HSB | The models and software versions of the active and standby ACs must be the same. | The active/standby switchover is implemented rapidly with little impact on services, which has high reliability. 1.Dual-link HSB: Only STA information is backed up between two ACs. An AP sets up a link with both active and standby ACs and exchanges management packets with both ACs. 2.VRRP HSB: AP, STA, and CAPWAP link information are backed up. An AP sets up a CAPWAP link with an AC and then backs up the CAPWAP link information on the other AC. The AP exchanges packets with only one AC. User information is backed up in batches and synchronized in real-time, ensuring service continuity and high reliability. A standby AC can provide backup services for only one active AC. |
| Dual-link cold backup | The active and standby ACs can be of different models but must use the same software version. | It provides only the basic backup functions and has lower reliability than hot-standby backup. Dual-link cold backup does not back up STA information. An AP establishes a link with both active and standby ACs. During an active/standby switchover or a revertive switchover, STAs must go online again and services are temporarily interrupted. A standby AC can provide backup services for only one active AC. |
| N+1 backup | The active and standby ACs can be of different models but must use the same software version. | A standby AC can provide backup services for multiple active ACs, which reduces device purchase costs. However, this mode has lower reliability than hot-standby backup. N+1 backup is a cold backup mode and does not back up AP or STA information. An AP establishes a link with only one AC. During an active/standby switchover or a revertive switchover, the AP and STAs must go online again and services are temporarily interrupted. The service interruption time in N+1 backup mode is longer than that in dual-link cold backup mode. A standby AC can provide backup services for multiple active acts. |
