1. MPLS Basics: Good understanding of how MPLS works, including LDP and RSVP-TE.
2. VPN Services: Hands-on experience testing L3VPNs and L2VPNs (VPLS, VPWS, EVPN).
3. Routing Protocols: Robust knowledge of how BGP / MP-BGP, OSPF, and IS-IS build paths and neighbors.
4. Network Convergence: Experience testing fast failover mechanisms like BFD and FRR (Fast Reroute).
5. Testing Tools: Experience using hardware traffic tools like Ixia (IxNetwork) or Spirent, along with Wireshark.