applies for Vxlan tunnel interfaces, Vxlan-GPE tunnel interfaces, Tap and TapV2 interafaces.

example:
when vxlan-gpe interface is created with:
PUT http://localhost:8183/restconf/config/ietf-interfaces:interfaces/interface/vxlanGpeTun3
{

"interface": [
{
"name": "vxlanGpeTun3",
"description": "for testing purposes",
"type": "v3po:vxlan-gpe-tunnel",
"enabled": "true",
"link-up-down-trap-enable": "enabled",
"routing" :

{ "ipv4-vrf-id" : "0" }

,
"vxlan-gpe" :

{ "local" : "192.168.50.77", "remote" : "192.168.50.73", "vni" : "9", "next-protocol" : "nsh", "encap-vrf-id" : "0", "decap-vrf-id" : "0" }

}
]

}
after that we can read data from http://localhost:8183/restconf/operational/ietf-interfaces:interfaces-state/ however when reading concrete interface http://localhost:8183/restconf/operational/ietf-interfaces:interfaces-state/interface/vxlanGpeTun3 we get nullpointer exception

This is caused because in VPP the interface gets different name and trying to get sw_interface_dump with filter by wrong name returns empty response. 

We need to map hc2vpp interface name to VPP interface name and use that when dumping vxlan-gpe interface.