Day 12 / 63 · Network foundations
The life of a packet
Study notes based primarily on Jeremy’s IT Lab CCNA learning videos. Credit to Jeremy’s IT Lab for the source lessons and diagrams.
The life of a packet
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Day 12 - The life of a packet Saturday, August 22, 2026 2:50 PM 12. LIFE OF A PACKET EACH Network device's interfaces have a UNIQUE MAC Addresses. In a TCP HEADER SOURCE IP ADDRESS comes before DESTINATION IP ADDRESS while... in an ETHERNET HEADER DESTINATION MAC ADDRESS comes before SOURCE MAC ADDRESS When a HOST sends a packet to another HOST, the SOURCE or DESTINATION IP doesn't change - even though ROUTERS may change the ETHERNET HEADER (SRC/DEST MAC ADDRESSES). Day 12 - The life of a packet Saturday, August 22, 2026 2:50 PM 12. LIFE OF A PACKET EACH Network device's interfaces have a UNIQUE MAC Addresses. In a TCP HEADER SOURCE IP ADDRESS comes before DESTINATION IP ADDRESS while... in an ETHERNET HEADER DESTINATION MAC ADDRESS comes before SOURCE MAC ADDRESS When a HOST sends a packet to another HOST, the SOURCE or DESTINATION IP doesn't change - even though ROUTERS may change the ETHERNET HEADER (SRC/DEST MAC ADDRESSES). Day 12 - The life of a packet Saturday, August 22, 2026 2:50 PM 12. LIFE OF A PACKET EACH Network device's interfaces have a UNIQUE MAC Addresses. In a TCP HEADER SOURCE IP ADDRESS comes before DESTINATION IP ADDRESS while... in an ETHERNET HEADER DESTINATION MAC ADDRESS comes before SOURCE MAC ADDRESS When a HOST sends a packet to another HOST, the SOURCE or DESTINATION IP doesn't change - even though ROUTERS may change the ETHERNET HEADER (SRC/DEST MAC ADDRESSES). Day 12 - The life of a packet Saturday, August 22, 2026 2:50 PM 12. LIFE OF A PACKET EACH Network device's interfaces have a UNIQUE MAC Addresses. In a TCP HEADER SOURCE IP ADDRESS comes before DESTINATION IP ADDRESS while... in an ETHERNET HEADER DESTINATION MAC ADDRESS comes before SOURCE MAC ADDRESS When a HOST sends a packet to another HOST, the SOURCE or DESTINATION IP doesn't change - even though ROUTERS may change the ETHERNET HEADER (SRC/DEST MAC ADDRESSES). Day 12 - The life of a packet Saturday, August 22, 2026 2:50 PM 12. LIFE OF A PACKET EACH Network device's interfaces have a UNIQUE MAC Addresses. In a TCP HEADER SOURCE IP ADDRESS comes before DESTINATION IP ADDRESS while... in an ETHERNET HEADER DESTINATION MAC ADDRESS comes before SOURCE MAC ADDRESS When a HOST sends a packet to another HOST, the SOURCE or DESTINATION IP doesn't change - even though ROUTERS may change the ETHERNET HEADER (SRC/DEST MAC ADDRESSES).