Bug ID 757827: Allow duplicate FQDN ephemeral create/delete for more reliable FQDN resolution

Last Modified: Jul 31, 2020

Bug Tracker

Affected Product:  See more info
BIG-IP LTM(all modules)

Known Affected Versions:
12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3, 12.1.3.1, 12.1.3.2, 12.1.3.3, 12.1.3.4, 12.1.3.5, 12.1.3.6, 12.1.3.7, 12.1.4, 12.1.4.1, 12.1.5, 12.1.5.1, 12.1.5.2, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0, 13.1.0.1, 13.1.0.2, 13.1.0.3, 13.1.0.4, 13.1.0.5, 13.1.0.6, 13.1.0.7, 13.1.0.8, 13.1.1, 13.1.1.2, 13.1.1.3, 13.1.1.4, 13.1.1.5, 13.1.3, 13.1.3.1, 14.0.0, 14.0.0.1, 14.0.0.2, 14.0.0.3, 14.0.0.4, 14.0.0.5, 14.0.1, 14.0.1.1, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.5, 14.1.0.6, 14.1.2, 14.1.2.1, 14.1.2.2, 14.1.2.3, 14.1.2.4, 15.0.0, 15.0.1, 15.0.1.1, 15.0.1.2

Fixed In:
15.1.0, 15.0.1.3, 14.1.2.5, 13.1.3.2

Opened: Feb 06, 2019
Severity: 3-Major

Symptoms

When using FQDN nodes and pool members, ephemeral pool members may not be created as expected immediately after a configuration-load or BIG-IP reboot operation.

Impact

When this issue occurs, some subset of ephemeral pool members may not be created as expected. As a result, some pools may not have any active pool members, and do not pass traffic. This issue, when it occurs, may persist until the next DNS queries occur for each FQDN name, at which point the missing ephemeral pool members are typically created as expected. Using the default FQDN interval value of 3600 seconds, such downtime lasts approximately one hour.

Conditions

This may occur on affected BIG-IP versions when: -- Multiple FQDN names (configured for FQDN nodes/pool members) resolve to the same IP address. -- DNS queries to resolve these FQDN names occur almost simultaneously. -- The BIG-IP version in use contains the fix for ID 726319 :: Bug ID 726319: 'The requested Pool Member ... already exists' logged when FQDN resolves to different IP addresses :: https://cdn.f5.com/product/bugtracker/ID726319.html. The occurrence of this issue is very sensitive to timing conditions, and is more likely to occur when there are larger numbers of FQDN names resolving to a common IP address.

Workaround

To minimize the duration of time when pools may be missing ephemeral pool members, configure a shorter FQDN interval value for the FQDN nodes ('##' is the desired number of seconds between successive DNS queries to resolve the configure FQDN name): tmsh mod ltm node fqdn-node-name { fqdn { interval ## } }

Fix Information

When using FQDN nodes and pool members, ephemeral pool members are now created as expected following a configuration-load or BIG-IP reboot operation. However, messages similar to the following may be logged when the DNS server returns a different set of IP address records to resolve the FQDN name: -- err mcpd[20479]: 01020066:3: The requested Node (****) already exists in partition ****. -- err mcpd[20479]: 01020066:3: The requested Pool Member (****) already exists in partition ****. These are benign messages that do not affect BIG-IP functionality.

Behavior Change