Tested using the VPP ML2 driver and openstack on one node. The issue presents itself as a VM failing to get a DHCP address or even using a static IP is unable to ping. Packets are able to flow from the kernel side into VPP but not out from VPP to kernel/linux space.

Openstack Steps:

• Create neutron net/subnet 'vppnet'
• Create 2 VMs attached to vppnet
• Test VMs both have DHCP addresses by pinging from within namespace
• Delete one of the VMs
• Create neutron net/subnet 'vppnet2'
• Create 1 VM attached to vppnet2
• Test DHCP address … This should have succeeded but fails

Following is the API (stripped) output:
SCRIPT: sw_interface_set_flags sw_if_index 2 admin-up link-up
SCRIPT: create_vlan_subif sw_if_index 2 vlan_id 1311
SCRIPT: l2_interface_vlan_tag_rewrite sw_if_index 3 vtr_op 3 push_dot1q 0 tag1 0 tag2 0
SCRIPT: sw_interface_set_flags sw_if_index 3 admin-up link-up
SCRIPT: bridge_domain_add_del bd_id 5678 flood 1 uu-flood 1 forward 1 learn 1 arp-term 0
SCRIPT: sw_interface_set_l2_bridge sw_if_index 3 bd_id 5678 shg 0 enable
SCRIPT: tap_connect tapname vpp489414bc-fc mac fa:16:3e:91:b2:a0
SCRIPT: sw_interface_set_l2_bridge sw_if_index 4 bd_id 5678 shg 0 enable
SCRIPT: sw_interface_set_flags sw_if_index 4 admin-up link-up
SCRIPT: create_vhost_user_if socket /tmp/526f6984-34fc-4f34-a15d-f50631b29b9c
SCRIPT: sw_interface_set_l2_bridge sw_if_index 5 bd_id 5678 shg 0 enable
SCRIPT: sw_interface_set_flags sw_if_index 5 admin-up link-up
SCRIPT: create_vhost_user_if socket /tmp/ce05a621-dab5-480d-a175-1994df24e061
SCRIPT: sw_interface_set_l2_bridge sw_if_index 6 bd_id 5678 shg 0 enable
SCRIPT: sw_interface_set_flags sw_if_index 6 admin-up link-up
SCRIPT: delete_vhost_user_if sw_if_index 6
SCRIPT: sw_interface_set_flags sw_if_index 2 admin-up link-up
SCRIPT: create_vlan_subif sw_if_index 2 vlan_id 1312
SCRIPT: l2_interface_vlan_tag_rewrite sw_if_index 6 vtr_op 3 push_dot1q 0 tag1 0 tag2 0
SCRIPT: sw_interface_set_flags sw_if_index 6 admin-up link-up
SCRIPT: bridge_domain_add_del bd_id 5679 flood 1 uu-flood 1 forward 1 learn 1 arp-term 0
SCRIPT: sw_interface_set_l2_bridge sw_if_index 6 bd_id 5679 shg 0 enable
SCRIPT: tap_connect tapname vpp60b4a9db-bd mac fa:16:3e:73:6d:18
SCRIPT: sw_interface_set_l2_bridge sw_if_index 7 bd_id 5679 shg 0 enable
SCRIPT: sw_interface_set_flags sw_if_index 7 admin-up link-up
SCRIPT: create_vhost_user_if socket /tmp/6879d52f-8c20-479c-af48-330d6d94eeb7
SCRIPT: sw_interface_set_l2_bridge sw_if_index 8 bd_id 5679 shg 0 enable
SCRIPT: sw_interface_set_flags sw_if_index 8 admin-up link-up