i tought it is very easy and understandable and that nobody actually needs a tutorial, but lately a lot of ppl have asked me how to do that.
Lot of ppl on Luigi's forum (aluigi.org) have also asked that.
so i tought i will write a tutorial on how to change your IP address IF it is possible (it means if you have dynamic ip address).
This tutorial contains:
- 1. what is dynamic and static IP address.
2. how does cable modem and router work.
3. how to change ip when you are using cable modem
4. how to change ip when you are using ADSL (phone line).
Dynamic IP - to make it understandble to ppl. Dynamic IP address can be changed or sometimes changes on its own after lease expires.
Static IP - your IP does not change. only way to change it, is to ask your ISP (internet service provider) to change it.
Here is link to wikipedia page that explains -IP Address- and also long explaination on what is dynamic and static ip.
2.
This part is written by SomaFM on Luigi's forum:
now this part is covered and i don't need to explain it again.This is a discussion continued from another thread. But we were starting to hijack the thread and go off-topic, so I figured I would start a new one with all the information I discovered about how docsis cable modems work. I hope you enjoy... and if I made a mistake anywhere let me know!
After doing further research into the topic, it appears that this is how the all cablelabs docsis approved modems work:
1) Cable modem is powered on. It sends out a BOOTP request. The CMTS on the cable provider's side will send a BOOTP reply that contains various information such as a config file name, tftp server, time server, syslog server, etc.
2) The cable modem looks at the BOOTP reply with all that nice information, and uses it in the following way:
- It connects to the TFTP server, and downloads the config file mentioned.
- It uses the time server to update it's clock (considering that it doesn't know the correct time when it boots up). This allows for accurate logs that can be sent to the syslog server.
3) The config file is a binary file that is written specifically for DOCSIS modems. I can give you samples of one, but there are plenty online. There is also a free tool on sourceforge that allows encoding/decoding of config files (http://docsis.sourceforge.net). The config file must be binary so that the cable modem can read it, so in order to edit an existing config file you might use that tool to decode it first. The config file contains information such as:
- NetworkAccess: this is a value set to 0 or 1 which defines if the modem can access the ISPs network and pass on DHCP requests and what not.
- MaxCPE: this defines how many CPE devices that can exist on the customer's side. In many cases, it's only 1 (so you can't get more than 1 public IP!)... but often times cable ISPs allow more than 1 just to alleviate the complaining customers who can't get an IP because they switched computers (new NIC) or something similar... and never restarted the modem to clear the cpe mac address ties. Lucky for me, my ISP allows for around 7-10 CPE devices. So yes, I can get that many public IPs. This is most likely a problem on their end considering I am a residential customer, but I am not going to say anything :). Plus, they know exactly how many CPE devices you are currently using, and I can assure you that logs are kept. So don't do anything that is going to get your internet shut off.
- Speeds: This isn't an exact variable, but in general, the config file also specifies what speeds (upload, download) your modem can have. This is where we get into spoofing the TFTP server so you can generate a custom config file, and uncap your speeds! Yes, it is possible to use your own config file, but it is very hard nowadays. Cable modem "speed uncapping" was a popular concept back in the day with particular modems, so if you wan't to know more about it and how it's done, do a Google search. But as of today, it's pretty tough to do (although it's still possible). It basically involves spoofing the tftp server so that your modem downloads a config file from you, rather than from the ISP. Be warned, this is another thing that will probably get your service terminated if you do it. They know how much bandwidth you're using, they aren't stupid! If you're using 10MBps when your account is only specified for 2MBps, you're going to get in trouble.
- The config file contains a lot of other cool information, but doing some Google searches can tell you more about what it contains.
4) So now you're modem is powered on and it has a config file! If NetworkAccess is set to 1 in the config file, your modem is authorized to talk on the ISP's cable modem network, and can relay DHCP requests from any client devices connected to the modem. You can get as many DHCP leases for your client devices up to whatever MaxCPE was set to. Once a CPE device has a public IP, you are officially online. Congratulations.
Other useful information/clarifications:
- The config file that you download is determined by your HFC MAC address. So when your modem sends that BOOTP request, the CMTS looks at the HFC MAC address and says: "oh, that's a residential customer. he gets the config file residential.bin which allows for 3MBps/256Kbps, with a maximum of 2 CPE devices!". The CMTS may also say "I don't recognize this MAC as a customer!... he get's disabled.bin which gives him no network access and 0 MaxCPE devices!"
- Docsis modems are required to make use of snmp. This can allow the customer to see useful information such as the tftp server's IP address, config file name, etc. that is normally not visible on the ethernet side of the modem. Docsdiag is a good/free tool for querying such information from the modem. However, the docsis config file can specify that only certain IP ranges can request to see the snmp info, thus blocking out customers from getting the data. My ISP does this; however, they didn't a while ago when docsdiag worked perfectly :P. I guess they are learning how to better secure themselves.
- Docsis has many versions: 1.x, 2.0, 3.0... and all may have slightly different ways of operating. 3.0 is fairly new and isn't much deployed yet. 2.0 seems to be the most common right now, while 1.x versions are fading out of networks.
Hope some of this was useful or interesting to someone. If I made a mistake, or was confusing anywhere, let me know and I will fix it. A lot of research came from Google searches, considering that some DOCSIS specs are actually kept undisclosed to the public, and are protected under a vendor NDA. However, you can download PDFs of some docsis specs from cablelabs's website (http://www.cablelabs.com/).
now how does DSL (digital subscriber line) connection work. unlike cable connection it is not mac address based. When you connect your modem/router to a DSL line then your modem will be connected to your phone company (also your ISP). So now you will need valid username:password to be able to use internet. You do not need to insert them manually, because your modem/router will do it for you. This is the basic way how it works.
NOTE - DSL may use mac based ip too, but most of the case it is user:pass
3.
ok when you are using cable modem, then all info you need to change IP is already in Soma's post.
-switch off your modem (pull out power). and wait for 1-2mins, after you plug it back in, you should have new ip
-change your computer's mac address (you can use TMAC or some other MAC changer). sometimes you may need to turn modem off first and then change your computer's MAC.
-renew your ip.
- a. go to startmenu
b. select RUN
c. type "cmd" in there and hit enter
d. now type "ipconfig /renew" into cmd window and hit enter.
4.
Changing IP when you use DSL line is easier, because it is not MAC address based. So in other words, each time you disconnect, you will get new IP address. I do not know exactly how it works when you have only ADSL modem, not router.
to me it takes only 3-5 seconds to chagne IP address. I will simply go to my router settings and click disconnect. this disconnects me from ISP and then after 3-5 seconds i click connect and i have new IP.
- if you have ADSL modem and it does not have disconnect option, simply turn power off in modem and wait for few seconds.
- if you have ADSL modem (not router), then renewing your ip may work (look above). IF you have router, then renewing ip will definetly NOT work, because it will only renew IP that is between router and your computer.
- using ADSL, you can also try the computer MAC address change, but i dont think it would work either.
best way is to simply disconnect internet or turn power off in your modem/router.
If you are unable to change IP using all those methods, then contact your ISP (internet service provider) and ask if you have static or dynamic IP. in 99% of cases you will have dynamic ip, because static IP comes as a service usually and you need to pay extra to get static IP.
