Configure PMTUD in IBM i

Verify or Allow Path MTU discovery (IPPATHMTU) Settings:

Path MTU discovery allows for dynamic MTU adjustment, on a per connection basis, to maximize network throughput.

Using IBM i 5250 Terminal: 

1. Login to the IBM i VM QSECOFR profile
2. Enter CHGTCPA & F4 on IBM i Command line. The Path MTU discovery parameters will be displayed.
3. Change the Enablement value to *YES or *DFT

Optionally, the default interval value of 10 can be changed by editing the interval and pressing ENTER.

You can also perform the same using the command CHGTCPA IPPATHMTU(*YES 10)