Forum Discussion
With version 11.5.1 ltm doesn't preserve client source port, it changes it.
i understand it is due to hardware architecture and cmp. source port has to be changed to make return traffic going to the same tmm.
sol14358: Overview of Clustered Multiprocessing (11.3.0 and later)
https://support.f5.com/kb/en-us/solutions/public/14000/300/sol14358.html
there is request for enhancement to implement preserve-strict for nat configuration but it is not yet implemented.
ID441079 - [RFE] Add "preserve-strict" option to NAT object to preserve source port strictly
anyway, could it be possible to use virtual server with preserve strict instead of nat?
sol11003: Configuring source port preservation for virtual servers
https://support.f5.com/kb/en-us/solutions/public/11000/000/sol11003.html