GTM - Topology load balancing failover when one pool is down

give the  BIGIP version,  and the configuration of GTM wideip and gslb pool. In wideip Advanced>>Load Balancing Decision Log,  Check all the options. You can see why this pool member is selected in the /var/log/ltm

After testing, the reason why wideip cannot rollback and skip tcp down gslb pool is related to the settings of Preferred, Alternate, and Fallback in gslb pool.
1. If gslb pool_ A is manually disabled by the administrator, wideip will skip disabled gslb pool_A and automatically selected Status "up" gslb pool_ B
2. If gslb pool_ A  all pool members are disabled by the administrator or all pool members tcp monitor down, wideip will automatically fallback to the Status "up" gslb pool_ B need to do this steps:

wideip name Load Balancing Method set "Topology", Pools is ["gslb pool_A", "gslb pool_B"]

gslb pool_A,pool_B Load Balancing Method, "Preferred" set Round Robin, "Alternate" set None, "Fallback" set Topology

root@(f5)(cfg-sync Standalone)(Active)(/Common)(tmos)# list gtm wideip a www.bestpay.com.cn
gtm wideip a www.bestpay.com.cn {
    aliases {
        mapi.bestpay.com.cn
    }
    load-balancing-decision-log-verbosity { pool-selection pool-traversal pool-member-selection pool-member-traversal }
    pool-lb-mode topology
    pools {
        gslb_pool_bestpay_ctc_v4 {
            order 0
        }
        gslb_pool_bestpay_cuc_v4 {
            order 1
        }
    }
    topology-prefer-edns0-client-subnet enabled
}



root@(f5)(cfg-sync Standalone)(Active)(/Common)(tmos)# list gtm pool a gslb_pool_bestpay_ctc_v4 
gtm pool a gslb_pool_bestpay_ctc_v4 {
    alternate-mode none
    fallback-mode topology
    members {
        DC-2-GTM-ipv4:/Common/vs_ctc_97_22 {
            disabled
            member-order 0
        }
        DC-2-GTM-ipv4:/Common/vs_ctc_97_23 {
            disabled
            member-order 1
        }
    }
}
root@(f5)(cfg-sync Standalone)(Active)(/Common)(tmos)# list gtm pool a gslb_pool_bestpay_cuc_v4 
gtm pool a gslb_pool_bestpay_cuc_v4 {
    alternate-mode none
    fallback-mode topology
    members {
        DC-2-GTM-ipv4:/Common/vs_ctc_98_22 {
            member-order 0
        }
        DC-2-GTM-ipv4:/Common/vs_ctc_98_23 {
            member-order 1
        }
    }
}