im trying to find the reason why cisco switches have a base mac-address and one for each port?? Can anyone help me to understand this..
The MAC address is the "hardware address" which uniquely identifies a virtual device (such as an SVI or loopback interface), a host, a port or what-have-you at Layer 2 of your network.
These extra MAC addresses are utilized by managed devices (such as Cisco switches) to provide additional functionality beyond that of a "dumb" switch or hub.
Understanding the 7-Layer OSI Networking Model is critical to your understanding and troubleshooting of networking issues.