What is the difference between IP Address, Mac Address and Default gateway?

The difference is this. Your device when connecting to a network has two things unique to it. The MAC address and the IP address. Different devices care about different parts of that information. Your switch cares about MAC address, that's how it decides what machine is on what port and where to send traffic. This is different from a hub as a hub doesn't care and just sends every packet to every port which is as ineffiecent as it sounds. Your IP address is tied to your MAC so other devices won't be assigned the same IP address by your DHCP server (it's what gives your machine it's IP address, typically integrated with your home router). There are ways around this and some scenarios where it's desired but if you're asking this question it doesn't apply to you. Default gateway is the route of last resort. If your computer (Mymachine.mynet.com) wants to talk to another computer named Server.mynet.com it does a few things. First it checks it hosts file to see if it knows the IP address for the machine so it doesn't waste time asking a DNS server what the IP is, if it doesn't find it in the hosts file it then checks its name cache which is dynamically built each time the machine is started. That's what makes your machine snappy when you enter a URL in your browser. The first time you head to a website it usually takes a few seconds to come up, this is because the first thing it has to do is find out where it is by asking a DNS server, which takes much longer than retrieving from a local cache on your machine. Finally if it can't find the DNS record in either hosts or the local cache it will THEN ask an external DNS server what the IP is. This is where MAC address, your machine's routing table, and default gateway come into play. Your machine has now gotten the IP address from any of the sources I said, then it sends a packet with a MAC address (if it knows it) and an IP address. If the switch recognizes the MAC address it forwards the packet to the correct machine. If it doens't know the MAC address it will then send the packet to the router which looks at the IP address and then checks its routing table to see if it knows how to get to the correct network. If it doesn't find the route to the correct network it sends the packet to the default gateway for further routing. If the address exists on the net and isn't a unroutable private address (10.x.x.x, 192.168.x.x,172.16-31.x.x) it sends it on to its destination bouncing through whatever routers advertise the correct route. Your machine on a typical home network has an INTERNAL IP address of 192.168.x.x given out by DHCP and your router does what's called NAT (basically it turns your 192.168.x.x into something publically routable like 72.22.12.12). I've done my best to explain what these are while keeping it simple! Hope this helps!

IP ("logical) address is equivalent to a zip code. There are thousands of different ones out there, you can change it at any time you want, and there's anywhere from 2-200 other people with the exact same IP address as you do. It is not unique in any way. MAC (physical) address is your physical computer's unique address. No two MAC addresses in the world are the same. It is stored as a part of the NIC (network interface card). MAC addresses are used to get the message to the correct computer in a network. The MAC address is like your street address. Default Gateway is the address configured into a computer's IP address settings specifying the address of a router to which the computer can send all packets destined for other networks. The default gateway in a computer's IP address settings must be set to the address of a router to which the computer can send all packets destined for other networks. The default address is not always the routers address, it must be set to the routers address or the packets (information) will just get sent back to it. If you are trying to see your address numbers, just pull up the command prompt (cmd.exe) and type "ipconfig /all" and it'll give you the info you need. If you are worried about somebody getting into your network via Wireshark or Network Stumbler, just make sure your firewall and antivirus are up to date and turned on.