GTM - Topology load balancing failover when one pool is down

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

Overview of BIG-IP DNS Topology records (11.x - 17.x) (f5.com)

After testing with BIGIP VE, when the wideip LB mode is topology, it only considers the following bound gtm pool to calculate the corresponding score according to the topology algorithm. gtm pool A is 200 points, and gtm pool B is 20 points, so the gtm pool A with 200 points is highest selected, regardless of the up/down status of the gtm pool at wideip level(when the administrator disables the gtm pool, will skip the gtm pool disabled by the administrator and directly select the next gtm pool)
If the fallback of the gtm pool is set to None or Topology, gtm pool A  Preferred Round Robin failed because no active pool members are available at the gtm pool level, and "Alternate" set None, "Fallback" set None or Topology, it will fallback to topology choose lower points status "up" gtm pool pool_B 

If the fallback is set to Return to DNS, it will fallback to dns bind to resolution, and all pool members in gtm pool A and pool B will be returned as A records(such as A1,A1, B1, B2)

fallback set "None", log:

[mapi.bestpay.com.cn A] 
[matched topology record (ldns:(region:/Common/all_ctc), server:(region:/Common/Region_CTC_GSLB_Pool), score:2000) to pool (gslb_pool_bestpay_ctc_v4)] 
[matched topology record (ldns:(region:/Common/Other_Region), server:(region:/Common/Region_CUC_GSLB_Pool), score:5) to pool (gslb_pool_bestpay_cuc_v4)] 
[topology selected pool (gslb_pool_bestpay_cuc_v4) - topology score (5) is higher] 
[topology selected pool (gslb_pool_bestpay_ctc_v4) - topology score (2000) is higher] 
[topology selected pool (gslb_pool_bestpay_ctc_v4) with the highest topology score (2000)] 
[topology selected pool (gslb_pool_bestpay_ctc_v4)] 
[pool member select check failed (vs_ctc_97_23:58.213.97.23) - pool member is disabled] 
[pool member select check failed (vs_ctc_97_22:58.213.97.22) - pool member is disabled] 
[round robin failed to select a pool member] 
[failed to select pool member by preferred load balancing method] 
[Using none load balancing method] 
[failed to select pool member by alternate load balancing method] 
[Using none load balancing method] 
[failed to select pool member by fallback load balancing method] 
[topology selected pool (gslb_pool_bestpay_cuc_v4) - topology score (5) is higher] 
[topology selected pool (gslb_pool_bestpay_cuc_v4) with the highest topology score (5)] 
[topology selected pool (gslb_pool_bestpay_cuc_v4)] 
[pool member check succeeded (vs_ctc_98_23:58.213.98.23) - pool member state is available (green)] 
[round robin selected pool member (vs_ctc_98_23:58.213.98.23)] 

fallback set "Topology", log:

[mapi.bestpay.com.cn A] 
[matched topology record (ldns:(region:/Common/all_ctc), server:(region:/Common/Region_CTC_GSLB_Pool), score:2000) to pool (gslb_pool_bestpay_ctc_v4)] 
[matched topology record (ldns:(region:/Common/Other_Region), server:(region:/Common/Region_CUC_GSLB_Pool), score:5) to pool (gslb_pool_bestpay_cuc_v4)] 
[topology selected pool (gslb_pool_bestpay_ctc_v4) - topology score (2000) is higher] 
[topology skipped pool (gslb_pool_bestpay_cuc_v4) - topology score (5) is not higher] 
[topology selected pool (gslb_pool_bestpay_ctc_v4) with the highest topology score (2000)] 
[topology selected pool (gslb_pool_bestpay_ctc_v4)] 
[pool member select check failed (vs_ctc_97_23:58.213.97.23) - pool member is disabled] 
[pool member select check failed (vs_ctc_97_22:58.213.97.22) - pool member is disabled] 
[round robin failed to select a pool member] 
[failed to select pool member by preferred load balancing method] 
[Using none load balancing method] 
[failed to select pool member by alternate load balancing method] 
[pool member select check failed (vs_ctc_97_22:58.213.97.22) - pool member is disabled] 
[pool member select check failed (vs_ctc_97_23:58.213.97.23) - pool member is disabled] 
[topology failed to select a pool member] 
[failed to select pool member by fallback load balancing method] 
[topology selected pool (gslb_pool_bestpay_cuc_v4) - topology score (5) is higher] 
[topology selected pool (gslb_pool_bestpay_cuc_v4) with the highest topology score (5)] 
[topology selected pool (gslb_pool_bestpay_cuc_v4)] 
[pool member check succeeded (vs_ctc_98_22:58.213.98.22) - pool member state is available (green)] 
[round robin selected pool member (vs_ctc_98_22:58.213.98.22)] 
[root@f5:Active:Standalone] config # 

fallback set "Return to DNS", log:

[mapi.bestpay.com.cn A] 
[matched topology record (ldns:(region:/Common/all_ctc), server:(region:/Common/Region_CTC_GSLB_Pool), score:2000) to pool (gslb_pool_bestpay_ctc_v4)] 
[matched topology record (ldns:(region:/Common/Other_Region), server:(region:/Common/Region_CUC_GSLB_Pool), score:5) to pool (gslb_pool_bestpay_cuc_v4)] 
[topology selected pool (gslb_pool_bestpay_cuc_v4) - topology score (5) is higher] 
[topology selected pool (gslb_pool_bestpay_ctc_v4) - topology score (2000) is higher] 
[topology selected pool (gslb_pool_bestpay_ctc_v4) with the highest topology score (2000)] 
[topology selected pool (gslb_pool_bestpay_ctc_v4)] 
[pool member select check failed (vs_ctc_97_23:58.213.97.23) - pool member is disabled] 
[pool member select check failed (vs_ctc_97_22:58.213.97.22) - pool member is disabled] 
[round robin failed to select a pool member] 
[failed to select pool member by preferred load balancing method] 
[Using none load balancing method] 
[failed to select pool member by alternate load balancing method] 
[selected configured option Return To DNS]