what is the duplex host detection configuration?

1. Configure dual-host detection and exception interfaces (based on BFD)
Why configure dual-host detection?
(1)When all physical links of the VSL are disconnected abnormally, the secondary chassis considers that the main chassisis lost, and the secondary chassis is switched to the main chassis. On the network, two main chassis have identical configurations. The network is unavailable.
(2) After the dual-host detection mechanism is configured, the dedicated BFD link detects that a dual-host chassis exists based on the packets sent and received by the dual-host. The system selects achass is (standby chassis) according to the dual-host detection rule to enter the recovery mode. All ports are forcibly disabled except the VSL port, MGMT port, and the exception port specified by the administrator (reserved for Telnet when other ports on the device are shutdown).


Therefore, dual-host detection can prevent theabove faults and ensure that the network is still available (provided thatother devices are connected to the dual-core with redundant links).
VSU configuration:
Ruijie>en
Ruijie#config ter
Ruijie(config)# interface gi2/4/2
Ruijie(config-if-GigabitEthernet 2/4/2)# noswitchport ------> Configure interface 2 as a routing interface
Ruijie(config-if)# exit
Ruijie(config)# interface gi1/4/2
Ruijie(config-if-GigabitEthernet 1/4/2)# noswitchport ------> Configure interface 1 as a routing interface
Ruijie (config-if)# exit
Ruijie (config)# switch virtual domain 1 ------>Go to VSU parameter configuration
Ruijie(config-vs-domain)# dual-active detection bfd------> Enable BFD, which is disabled by default
Ruijie(config-vs-domain)# dual-active bfd interfacegi1/4 ------> Configure a pair of BFD detection interfaces
Ruijie(config-vs-domain)# dual-active bfd  interface gi2/4/2
Ruijie(config-vs-domain)# dual-active excludeinterface ten1/1/2 ------> Specify an exception interface, exclude the upperroute interface, and use telnet when dual hosts occur
Ruijie(config-vs-domain)# dual-active excludeinterface ten2/1/2 ------> Specify an exception interface
2. Configure dual-host detection (based on aggregation port detection)
The best way to prevent dual hosts on multiple Vsus is to use aggregation detection. In this way, multiple BFD lines do not need to be connected in pairs. Aggregation detection requires only n lines. However, the premise is that the linked access switch is a Ruijie device, so as to ensure that the private packets of Ruijie can be forwarded normally.


Note: If the MAD configuration is required, the access switch must support the MAD function; otherwise, the MAD function cannot be used for dual-host detection.
After the VSU is created, run the following command:
VSU switch configuration:
Ruijie(config)# switch virtual domain 1
Ruijie(config-vs-domain)# dual-active detectionaggregateport
Ruijie(config-vs-domain)# dual-active interfaceaggregatePort 1
Ruijie(config-vs-domain)# exit
On  accessswitch:
Ruijie(config)#interface aggregateport 1
Ruijie(config-if-Aggregate Port 1)# dad relay enable
Ruijie(config-if-Aggregate Port 1)# exit