What is L1, L2, L3 in network engineer support tiers and how do responsibilities differ?

L1 handles ticket logging, basic troubleshooting (ping, traceroute), password resets, and escalates unresolved issues—typically 6-12 months experience. L2 engineers diagnose routing protocol failures (OSPF neighbor states, BGP path selection), VLAN misconfigurations, and firewall ACL issues—requires 2-4 years and CCNA/CCNP. L3 architects solutions, handles complex multi-vendor integrations, capacity planning, and mentors junior staff—demands 5+ years with CCIE or equivalent. Bangalore employers like Cisco India, Aryaka, and Akamai clearly separate these tiers in NOC/TAC roles. Interview tip: Be honest about your tier—claiming L3 skills without design experience is immediately evident in technical rounds.