loop create
set int ip address loop0 6.0.0.1/32
set int state loop0 up
set int state GigabitEthernet1b/0/0 up
set int ip address GigabitEthernet1b/0/0 192.168.1.1/24

create host-interface name vpp1
set int state host-vpp1 up
set int ip address host-vpp1 6.0.1.1/24

packet-generator new {
  name udp
  limit 512
  rate 1e4
  node ip4-input
  size 100-100
  interface loop0
  no-recycle
  data {
   UDP: 192.168.1.2 - 192.168.2.255 -> 192.168.1.1
   UDP: 4321 -> 1234
    length 72
    incrementing 100
  }
}
session enable