Please find this comparison first for the backup modes :Comparison of Backup Modes
The device supports hot-standby (HSB), dual-link cold backup, and N+1 backup modes. Table 1 compares the three backup modes.
Table 1 Comparing the three backup modesItem | VRRP HSB | Dual-Link HSB | Dual-Link Cold Backup | N+1 Backup |
|---|
| Implementation | The active and standby ACs have independent IP addresses, which are virtualized into one using VRRP. APs set up CAPWAP links with this virtual IP address. The active AC backs up information about APs, STAs, and CAPWAP links, and synchronizes such information to the standby AC through the HSB service. If the active AC fails, the standby AC takes over services. | An AP sets up an active and a standby CAPWAP link with the active and standby ACs, respectively. The active AC backs up only STA information and synchronizes such information to the standby AC through the HSB service. If the active AC fails, APs connected to it switch to the standby links and the standby AC takes over services. | An AP sets up an active and a standby CAPWAP link with the active and standby ACs, respectively. ACs do not back up or synchronize information. If the active AC fails, APs connected to it switch to the standby links and the standby AC takes over services. | An AP sets up a CAPWAP link with only one AC. ACs do not back up or synchronize information. If a master AC fails, APs connected to it set up CAPWAP links with the backup AC that takes over services. |
| Switchover speed | The switchover speed is fast, with little impact on services. The configuration of the VRRP preemption delay implements a faster switchover than other backup modes. | The AP status switchover is slow and occurs only when CAPWAP link disconnection timeout is detected. After the AP status is switched, STAs do not need to go offline and online again. | The AP status switchover is slow and occurs only when CAPWAP link disconnection timeout is detected. STAs need to go online again, and services are interrupted for a short period of time. | The AP status switchover is slow and occurs only when CAPWAP link disconnection timeout is detected. APs and STAs need to go online again, and services are interrupted for a short period of time, which is longer than the service interruption period in dual-link cold backup mode. |
| Deployment of active and standby ACs at different places | VRRP is a Layer 2 protocol and does not support deployment of active and standby ACs at different places. | Supported | Supported | Supported |
| Constraints | The models and software versions of the active and standby ACs must be the same. A standby AC can provide backup services only for one active AC. | The models and software versions of the active and standby ACs must be the same. A standby AC can provide backup services only for one active AC. | The software versions of the active and standby ACs must be the same. No constraint is placed on the AC model. A standby AC can provide backup services only for one active AC. | The software versions of the active and standby ACs must be the same. No constraint is placed on the AC model. A backup AC can provide backup services for multiple master ACs, reducing device investment. |
| Applicable scope | Scenarios that require high reliability, without the need for AC deployment at different places | Scenarios that require high reliability and AC deployment at different places | Scenarios that have low reliability requirements | Scenarios that have low reliability and low cost requirements |
You can refer to the reliability configuration guide for the details :
https://support.huawei.com/hedex/pages/EDOC1100008272AEH0312X/04/EDOC1100008272AEH0312X/04/resources/dc/dc_cfg_reliab_cd.html?ft=0&fe=10&hib=11.1.21&id=dc_cfg_reliab_cd&text=Reliability%20Configuration%20Guide&docid=EDOC1100008272
Regarding the license :
License Deployment in Backup Scenarios
For V200R005C10 and earlier versions, license synchronization between the active and standby ACs is not supported in any backup mode. The following table lists license deployment policies in different backup modes.Backup Mode | License Deployment Policy |
|---|
HSB | Dual-link hot standby (load balancing mode) | Load the license for the active and standby ACs separately. Each of the two licenses must meet the requirement for the AP quantity. |
Dual-link hot standby (active/standby mode) |
VRRP hot standby |
Dual-link cold backup |
N+1 backup | Apply for and load the license for each AC separately. Ensure that the number of APs supported by the license of the backup AC is not less than that supported by the license of any master AC. In this way, if any master AC fails, all APs on the faulty master AC can be switched to the backup AC. |
Please refere to this link for more details :
https://support.huawei.com/hedex/pages/EDOC1100008272AEH0312X/04/EDOC1100008272AEH0312X/04/resources/dc/dc_wlan_lg_0063.html?ft=0&fe=10&hib=10.2.7.5&id=dc_wlan_lg_0063&text=License%20Application%3A%20How%20Do%20I%20Configure%20Licenses%20for%20ACs%20in%20Backup%20Mode%3F&docid=EDOC1100008272
