Netstat will show open connections by IP and port. Nslookup will resolve domains to IP addresses (DNS). Ipconfig /all will show you the default gateway and your MAC addresses but not the MAC of another network device. arp -a will show the Address Resolution Protocol (ARP) table, which will include the ARP for your default gateway.
The Address Resolution Protocol (ARP) is a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address This mapping is a critical function in the Internet protocol suite ARP was defined in 1982 by RFC 826, which is Internet Standard STD 37 ARP has been implemented with many combinations of network and data link layer technologies, such as IPv4, Chaosnet, DECnet and Xerox PARC Universal Packet (PUP) using IEEE 802 standards, FDDI, X25, Frame Relay and Asynchronous Transfer Mode (ATM) IPv4 over IEEE 802