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Scoring Rubric - Networking

Score 0-1

  • Don't know the difference between IP and MAC addresses
  • Can't explain what DNS does

Score 2-3

  • Understand IP addresses, subnets (at a high level), and DNS
  • Know that TCP is reliable and UDP is not
  • Have used ping and maybe traceroute
  • Don't understand VLANs, routing, or ARP

Score 4-5

  • Can explain VLANs, subnetting (can calculate a /24 vs /16)
  • Know the OSI model layers (at least L2/L3/L4/L7)
  • Can use ip, ss, dig for basic troubleshooting
  • Understand the difference between access and trunk ports
  • Can explain what a default gateway is and why it matters
  • "You are here if you can": explain why two servers on different VLANs can't communicate without a router, and use dig to troubleshoot DNS

Score 6-7

  • Can troubleshoot layer-by-layer systematically
  • Understand ARP, MAC tables, and how switches learn addresses
  • Can use tcpdump to capture and analyze traffic
  • Know common failure modes: MTU black holes, duplex mismatch, asymmetric routing
  • Understand OSPF/BGP at a conceptual level (what they do, when they're used)
  • Can read and interpret Cisco show command output
  • Can configure Linux networking: static routes, VLANs, bonding
  • "You are here if you can": use tcpdump to prove a firewall is dropping traffic, explain why SCP hangs but SSH works (MTU), and read a Cisco routing table

Score 8

  • Can design network topologies (ToR/EoR, redundancy, VLAN schemes)
  • Understand NAT, PAT, and their implications for troubleshooting
  • Can debug complex routing issues (asymmetric paths, route leaking)
  • Know how network policies map to iptables/nftables rules in Kubernetes
  • Can set up and troubleshoot Linux bridges, VXLAN, or overlay networks
  • "You are here if you can": design a VLAN scheme for a new datacenter, debug an asymmetric routing problem, or explain how Kubernetes CNI plugins implement pod networking

Score 9

  • Deep understanding of TCP internals (window scaling, congestion control, TIME_WAIT)
  • Can debug at the packet level (analyze pcap files, understand protocol state machines)
  • Understand BGP route selection, OSPF area design, multicast
  • Can design and implement network segmentation for security compliance
  • "You are here if you can": analyze a pcap to find a TCP retransmission problem, design a BGP peering arrangement, or explain why TCP TIME_WAIT sockets accumulate