Networking Lab: Network Address Translation (NAT / NAPT) Table
Inspect private-to-public IP address and port mapping tables as LAN packets traverse an egress border router to public internet endpoints.
End-to-End Multi-Hop Packet Forwarding Engine
Trace a packet across Host A → Switch 1 → Router 1 → Router 2 → Switch 2 → Host B. Inspect dynamic ARP resolution, transparent MAC learning, routing table Longest Prefix Match (LPM), hop-by-hop L2 re-encapsulation, and TTL decrement.
Layer 2: Ethernet II Frame
Hop-by-Hop L2Note: Layer 2 MAC addresses change whenever the packet crosses a router boundary.
Layer 3: IPv4 Datagram
End-to-End L3If the packet starts at Host A with initial TTL = 64 and traverses 2 intermediate routers before arriving at Host B, what will the final received TTL value be?
Stage Explanation: Payload Creation & Route Check
Host A checks local subnet (192.168.1.0/24). Destination 192.168.2.20 is remote!Host A performs bitwise AND: (192.168.2.20 & 255.255.255.0) != (192.168.1.10 & 255.255.255.0). Destination is on an outside subnet, so Host A targets its Default Gateway (Router 1 Eth0).