IP Assign data

So, the MAC address is for network communication. Do LANs have methods for identifying computers beyond the MAC address? Is it assumed that a computer connected to the network is not trying to represent itself as another computer via the MAC address?
-Summary--->
My computer communicates with the domain server via various protocol and it identifies itself via MAC address. The domain assigns my workstation with an IP. This allows access to the internet. Does a LAN or can a LAN monitor other computer information? Wouldn't it be in the best interest of the network to try to monitor malicious use or other data to prevent malicious spoofing?

One more thing please,
Is IEEE 802.1 authentication the verification of the MAC or is it something additional? Smart Cards? What does this mean, "Verify as computer when computer information is available"?

the DHCP is enabled so the IP is static...

If the DHCP is enabled the IP is dynamic. It is very common for a DHCP server to give you the same address when your lease expires. Did you notice the Lease Obtained and Lease Expires at the bottom of your ipconfig /all output?

It is not uncommon to get the same IP for weeks or months or even years. It usually depends on how often the DHCP server might get rebooted.

That is true and is usually the case in networks where machines don't get moved around a lot.