To reproduce, add interface VXLAN without the port and then set the port.
set interfaces vxlan vxlan23 address '100.64.10.2/24' set interfaces vxlan vxlan23 remote '192.0.2.1' set interfaces vxlan vxlan23 source-address '192.0.2.5' set interfaces vxlan vxlan23 vni '23' commit set interfaces vxlan vxlan23 port '4789' commit
Get port 8472, expected port 4789
vyos@r1# ip -d link show dev vxlan23 12: vxlan23: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/ether 22:6e:6d:33:c5:6b brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 65535 vxlan id 23 remote 192.0.2.1 local 192.0.2.5 srcport 0 0 dstport 8472