From
RFC7348
- Source Port: It is recommended that the UDP source port number
be calculated using a hash of fields from the inner packet --
one example being a hash of the inner Ethernet frame's headers.
This is to enable a level of entropy for the ECMP/load-
balancing of the VM-to-VM traffic across the VXLAN overlay.
When calculating the UDP source port number in this manner,
it
is RECOMMENDED that the value be in the dynamic/private port
range 49152-65535 [
RFC6335].
If they followed the RFC. The source port should always be in the range of
Ephemeral ("Private") ports