Wireshark MAC IP Analysis: Uncovering the Mystery of Duplicate MAC Addresses

In the world of computer networking, there are certain scenarios that can raise eyebrows and spark curiosity. One such phenomenon is when multiple packets with different IP addresses but identical MAC addresses are transmitted from a single source. This article delves into an investigation using Wireshark to unravel the mystery behind this occurrence.

A recent experience with a computer running an embedded OS has led to this observation. The machine, equipped with 10 physical Ethernet ports, was transmitting data over a network to an XP embedded machine. Upon capturing packets using Wireshark, it became apparent that all packets sent from the embedded OS-based computer shared the same MAC address. This raised questions about the integrity of the MAC addresses and their association with IP addresses.

A closer examination revealed that each packet sent by the embedded OS-based computer was correctly paired with a unique IP address. However, the MAC addresses remained identical for all packets. This peculiar behavior led to an investigation into whether this was a common occurrence or if there was something amiss in the system configuration.

To shed more light on this issue, it's essential to understand how MAC addresses are typically utilized in computer networking. In most cases, each Ethernet port has its unique MAC address assigned by the manufacturer. When a device connects to a network, these MAC addresses help identify the source of incoming packets.

In this instance, however, the embedded OS-based computer was configured to assign unique IP addresses to each physical Ethernet port using the application. This setup ensured that each packet transmitted from a distinct port carried a corresponding unique IP address. When checked using the ifconfig command, it confirmed that each physical port had been assigned a unique MAC address.

The question remains: why did Wireshark captures show all packets transmitting with the same MAC address despite having different IP addresses? This anomaly suggests that either the application or the embedded OS was not utilizing the configured unique MAC addresses correctly.

Further investigation is required to determine the root cause of this issue. It's possible that there might be a bug in the embedded OS or the application that's preventing the use of individual MAC addresses. Alternatively, it could be an inherent limitation in the system's network configuration.

In conclusion, while Wireshark captures did reveal multiple packets with different IP addresses but identical MAC addresses, this behavior may not be as common as one might expect. The investigation has highlighted the importance of verifying MAC address assignments and their correspondence with IP addresses to ensure proper packet transmission and reception.

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