There were two systems:

system1, main system on which most of the configuration take place

system2, some configuration here

Configure IPv6 network.

Configure eth0 with a static IPv6 addresses as follows

Configure a Static IPv6 address in serverX as fddb:fe2a:ab1e::c0a8:64/64

Configure a Static IPv6 address in desktopX as fddb:fe2a:ab1e::c0a8:02/64

Both machines are able to communicate within the network fddb:fe2a:able/64

The changes should be permanent even after the reboot

On ServerX:

On DesktopX: