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Communication between two APIPA computers without DHCP Server

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On the last Saturday, I and my friend are trying to connect two computers directly using a USB cable and start communication between these two computers without the help of any external DHCP server. As I mentioned in my previous post we cannot use an ordinary USB cable to connect two computers directly. It may burn the USB port.

[ To know more about it please follow the link below.

http://www.corenetworkz.com/2009/10/can-i-connect-two-computers-using-usb.html ]

In this project, we avoid using the router or any other DHCP servers. As we are not using the Ethernet adapters we cannot set any static IP address. So without the presence of external DHCP server and static IP address our both computers will get APIPA from Windows Operating System.

[ To know more about APIPA please click on the link below.

http://www.corenetworkz.com/2008/02/how-to-resolve-issue-when-ip-getting-is.html ]

So the IP address our computers got was a 169.254.X.X range. Fortunately, the IP address gained by our computers were in the range 169.254.1.X and it started to communicate with each other.

It is sure that APIPA computers can communicate with each other as their subnet mask is 255.255.0.0 (Class B address). So as the subnet rules say the network address of APIPA is 169.254.0.1 and the broadcast address is 169.254.255.255. Any address comes in between this range can communicate with each other. Because it is a private IP address we cannot use APIPA to get the Internet connection to our computers. For Local networks and Intranet APIPA is enough.


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Unknown said…
The correct Network ID is 169.254.0.0 and the Broadcast ID is 169.254.255.255 the assignable addresses for this class B network are 169.254.0.1 to 169.254.255.254.
9:09 AM
Alex George said…
Thank you Exipheas,

You are absolutely right. The network id of APIPA is 169.254.0.0

While writing the network id on my post ,actually what was in my mind is the first valid IP address in APIPA. The first IP address is 169.254.0.1

I understand my second mistake (broadcast address). I don't know why did I made such an error while typing the post. I will edit that error soon. Once again my thanks to pin point the mistakes I made.
9:04 PM
Anonymous said…
Do you know if there is a way to determine the IP's of all connected stations?

Let's say I have 5 computers in a LAN and they assign themselves an IP by APIPA.
Now I can only access one machine (because the others are embedded systems), how can I find out the other IP addresses?

Thanks,
Alex
2:58 AM
Alex George said…
@ Alex

APIPA is assigned by the OS it self and there is no external DHCP server works for it. So I don't think there is any way to find the APIPA ip address of other computers in the LAN without checking each system manually.
9:37 PM
Anonymous said…
yo... love this !
3:18 PM
Unknown said…
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7:33 PM
Unknown said…
guys can you help, my hp pavillion cannot change the Ip 169.254.x.x i have already ipconfig/release=ok renew=error im using win7 the laptop can communicate trough other computer in the network that has an ip of 192.168.x.x my other pc can access the net. but the laptop cannot access internet help plz im troubleshooting this for 3 days and i have no luck...
11:26 PM
Admin said…
I recommend you to assign a static IP address in hp pavillion in 192.168.X.X range and check for the issue. To know more about this issue follow the link below.

How to Resolve APIPA
10:37 PM
Anonymous said…
Hi,the post is really good and informative.I have one doubt suppose there are five machines connected to a switch and 3 of them are getting ip address from DHCP server and 2 of them are getting the APIPA.So my question is will the 2 APIPA machines communicate with the other 3 machines? and will the 2 APIPA machines communicate each other please reply.
3:21 AM
Admin said…
1. Your APIPA machines cannot communicate with other 3 devices getting IP addresses from external DHCP server since they are in different network address.

2. APIPA machines connected in the same network can communicate each other
8:59 AM
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Alex George
Alex George has Engineering graduation in Computer Science and an MBA in Finance. He had been working as a senior Network Engineer for ten years. His specialization is in Cisco products. Traveling is one of his hobbies and visited various places as part of his onsite work. He visited different places as part of his onsite work like New York, Dubai, London, etc. Right now Alex is a director of one of the leading career development firms in India, which trains students for UPSC, SSC, and PSC examinations. He guides a lot of students to get selection for various prestigious institutions like CBI, Income Tax Department, etc. Alex George is a stock market investor and a very active intraday trader. Engineering Background: He has a B.Tech in Computer Science and Engineering and passed different network and security courses like CCNA, CCNP (Security), CEH, and various Microsoft certifications. Finance Background: Alex has an MBA in Finance. He is an active intraday trader and a Share Market Investor. Webmaster Skills: Alex is a blogger since 2004. He has a working knowledge of HTML, CSS, PHP, and JavaScrip.