Ensure that backup NHGs are honoured with NextHopGroup entries containing >1 NH.

• Connect ATE port-1 to DUT port-1, ATE port-2 to DUT port-2, ATE port-3 to DUT port-3, and ATE port-4 to DUT port-4.
• Create a L3 routing instance (VRF-A), and assign DUT port-1 to VRF-A.
• Create a L3 routing instance (VRF-B) that includes no interface.
• Connect a gRIBI client to the DUT, make it become leader and inject the following:
  • An IPv4Entry in VRF-A, pointing to a NextHopGroup (in DEFAULT VRF) containing:
    • Two primary next-hops:
      • IP of ATE port-2
      • IP of ATE port-3
    • A backup NHG containing a single next-hop pointing to VRF-B.
  • The same IPv4Entry but in VRF-B, pointing to a NextHopGroup (in DEFAULT VRF) containing a primary next-hop to the IP of ATE port-4.
• Add an empty decap VRF, DECAP_TE_VRF.
• Add 4 empty encap VRFs, ENCAP_TE_VRF_A, ENCAP_TE_VRF_B, ENCAP_TE_VRF_C and ENCAP_TE_VRF_D.
• Replace the existing VRF selection policy with vrf_selection_policy_w as in https://github.com/openconfig/featureprofiles/pull/2217
• Ensure that traffic forwarded to the destination is received at ATE port-2 and port-3. Validate that AFT telemetry covers this case.
• Disable ATE port-2. Ensure that traffic for the destination is received at ATE port-3.
• Disable ATE port-3. Ensure that traffic for the destination is received at ATE port-4.

rpcs:
  gnmi:
    gNMI.Get:
    gNMI.Set:
    gNMI.Subscribe:
  gribi:
    gRIBI.Get:
    gRIBI.Modify:
    gRIBI.Flush:

vRX