Forum Discussion
AltocumulusGTM - Topology load balancing failover when one pool is down
Cumulonimbusgive 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
}
}
}
AltocumulusHello,
We had the loggin already enabled and we use dthis to verify that the topology load balancing was selecting the pool with al lmemembers down:
[pool member check failed (Yyyyyyyy_RAS:y.y.y.y)]
[pool member (Yyyyyyyy_RAS:y.y.y.y) deleted persistence (y.y.y.y)]
[matched topology record (ldns:(region:/Common/Japan_RAS_VPN_region), server:(pool:/Common/Geneva_RAS_VPN_Pool), score:20) to pool (Geneva_RAS_VPN_Pool)]
[matched topology record (ldns:(region:/Common/Japan_RAS_VPN_region), server:(pool:/Common/Japan_RAS_VPN_Pool), score:200) to pool (Japan_RAS_VPN_Pool)]
[topology selected pool (Geneva_RAS_VPN_Pool) - topology score (20) is higher]
[topology selected pool (Japan_RAS_VPN_Pool) - topology score (200) is higher]
[topology selected pool (Japan_RAS_VPN_Pool) with the highest topology score (200)]
[topology selected pool (Japan_RAS_VPN_Pool)]
[pool member select check failed (Zzzzzzzz_RAS_VPN:z.z.z.z) - pool member is disabled]
[pool member select check failed (Yyyyyyyy_RAS:y.y.y.y) - pool member is disabled]
[round robin failed to select a pool member]
[failed to select pool member by preferred load balancing method]
[selected configured option Return To DNS]
We were using the default "Return to DNS" as the faillback load balancing method. If the Fallback load balancing method as topology, would this not only apply the topology rules ot the pool members of the pool. But I have not tested what you have suggest. I will test it when I can.
Many thanks,
Michael
- xuwen
Fallback load balancing method set None or Topology, result is the same(choose a lower points state "up" gtm pool for wideip)
The system will also check the up status of the gtm pool member when the persistence is enabled for wideip. Like LTM, if the pool member is down, it will be reselected
