You cannot change the MAC address they are permanent by design. You can modify them or "spoof " them which basically just tells the operating system to REPORT a different MAC address, but this doesn't replace the original MAC address. MAC addresses are PHYSICAL address' meaning they are specific to the physical device, in this case your router. For example some internet providers bind their service to a specific MAC address. If you get a new Network interface card (NIC) or router you will lose the service however you can spoof the MAC address so to the one recognized by the internet provider so you will get service. This is not permanent if you spoof the MAC of your NIC as soon as you reboot it will revert to the MAC address PHYSICALLY STORED on the card. If you spoof the MAC of your router as soon as the router is rebooted it will revert back to the MAC PHYSICALLY Stored in the router. MAC=PHYSICAL address
IP address is not physical it is LOGICAL, these can be changed permanently. Because IP addresses are LOGICAL they are not physically stored in the system like MAC addresses are. They can be static IP's meaning they will always stay the same, but most likely they are Dynamic meaning they change. Dynamic IP addresses are assigned with the DHCP protocol. In most cases you cannot change your REAL IP because the DHCP configurations are controlled by your Internet provider. You will see your IP as something like 192.168.0.1 but that is not your real IP it's just the IP your provider provided to you through a mask because there aren't enough ipv4 addresses to go around.. Your REAL IP is something different you can find it with Google. The main difference from your real IP and fake is that your REAL IP is what is used by the Wide Area Network (WAN), so that other routers can reach you, think of your real IP as you OUTSIDE Identity. Your IP that looks something like 192.168.0.1 is your Local Area Network (LAN) IP it is used so that you can be reached by other computers WITHIN YOUR LOCAL NETWORK, think of this as your INSIDE identity. It is unique within the LAN only but other peoples LAN will distribute IP's that are likely the exact same. If your at home and you have a router, that is your LAN other people connected to your LAN can reach you with your local IP, when you surf the internet your router converts your local IP to you REAL IP (NAT) to be used on the Wide Area network (WAN). The reason is bc there are now hundreds of millions of internet users, so obviously everybody cannot get their own. NAT or network address translation is a process where your router takes the local IP and converts the to the REAL IP given to the router, it is the same REAL IP for everybody within the LAN unless configured otherwise.
So now you can see that you can spoof your LAN IP but unless your internet provider allows it (which they likely don't) your REAL IP is still the same. To spoof either the MAC or IP address you use ipconfig (ifconfig for linux/mac osx). Your MAC is physically stored and CANNOT be permanently changed, Your IP can be permanently changed in but it is likely you won't be able to, permanently change your REAL or external IP you will have to request a static IP from your ISP.