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When to switch to Link Local Address


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#1 devprogrammer

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Posted 29 June 2018 - 07:14 PM

If a networking embedded device that has no routeable configuration but DHCP enabled and receives no response from any DHCP server in the network - should the device switch over to Link Local Addressing mode? IN such a case how is the DHCP request timeout is considered?

If not then when should a networking device gain a Link Local address?



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#2 sflatechguy

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Posted 01 July 2018 - 11:33 AM

Using a link local, or APIPA address will give it an IP address in the 169.254.1.0 to 169.254.254.255 range. That's fine, if there is at least one other device on that LAN that has an address in the range. Otherwise, the device will have the same issue -- it won't be able to communicate with any other device.

 

You're probably better off trying to determine why it's not getting an address from any of the DHCP servers. Is there a DHCP server on that local area network segment? If not, are the switches and/or routers set to allow or deny DHCP traffic?



#3 devprogrammer

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Posted 01 July 2018 - 11:55 PM

The Auto IP mode is subject to scenario and we do not want our device to be not configured / setup. Thus we are implementing device behavior specifically when plugged into network and being able to communicate by picking up an IP.

 

Hence as per the scenario  - we do enable DHCP but ensure that no server response to its request. What should be the state of the device and how long it should it wait for a response - is there any recommendations by any RFCs in networking?



#4 sflatechguy

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Posted 08 July 2018 - 10:00 AM

You have DHCP enabled on the device, but I have no info on how DHCP is configured. How long isthe device set to wait for a response before it falls back to the APIPIA address? In some scenarios, this can take as long as 1 minute.






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