I have a large batch of TCP/IP devices that I want to configure all identically. They all have identical IP address by default.
I connect a device directly to a PC, upload a configuration file to the device through it's built-in web interface, and disconnect the device.
My problem is that when I connect another device to the PC, I can't ping it or access it through a web browser. I need to change its IP address using a utility that allows me to do this. Then I can access it with a web browser and upload the config file. What I have found is that if I use a rotating range of IP address, say .121 through .128, I can go back and re-use the same addresses. I just can't use the same address too soon or it won't work.
Emptying the cache doesn't solve this. In fact, If I use the same address with a second device, I can't connect with another browser. In fact, I can't even ping it. Just waiting for some unknown amount of time fixes the issue, but then I have to wait again if I connect another device.
My question is, how can I get this to work so I can simply connect a device, upload the config file, disconnect the device, and connect the next device, without having to change its IP address?
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Answers by: bryanf | rodmar | tb714usr | awt
You need to clear the arp cache. If you are on a Windows box, open a command prompt and type arp -a. You will see a list of IP and mac addresses. Now type arp -d * and then do the arp -a again. If you had more than one entry in the list at first, you should now see only one. Try your devices. Every time you connect a computer to a device with an IP address, that IP address gets tied to a mac address in the arp table. This table flushes automatically, but not immediately. Let me know if it works.