HeaderStack CCNA
Step through encapsulation on the path from PC to server. Click any PDU block to expand header fields — Ethernet frame border wraps L3/L4/L7; FCS sits separately on the right.
Scenario
One end-to-end story: DNS resolves the name, ARP finds the gateway MAC, TCP completes the 3-way handshake, HTTP is encapsulated, the switch forwards on MAC, the router rewrites Layer 2 and decrements TTL, and the server de-encapsulates.
Path
DNS query at Layer 7
L2 frame border · L3 packet · L4 segment · L7 payload · trailer — click any block
Explanation
① DNS — Browser needs an IP address
The user typed www.example.com. The resolver builds a DNS query — no transport headers yet.
PC builds DNS query before any transport headers exist
Click Ethernet Header, IPv4 Header, or any block above to expand field details.