https://devzone.nordicsemi.com/f/nordic-q-a/98646/extended-address-of-sed-changed-abruptlyHi, I have seen the ExtAddr of a SED device changed abruptly. The SED was connected through a router before this happened. This is very rare, but this could be a catastrophic failure for us. What I want to know is 1. I am using &#39; otLinkGetExtendedAddressen-USTelligent Community 13Wed, 12 Apr 2023 14:18:29 GMThttps://devzone.nordicsemi.com/thread/420003?ContentTypeID=1Wed, 12 Apr 2023 14:18:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c46cec1c-27b3-474d-b2ed-e9511795eb72Marte Myrvold<p>Hi Kaushalya,</p> [quote user=""]1. I am using &#39;<span>otLinkGetExtendedAddress</span><span>(</span><span>openthread_get_default_instance</span><span>())&#39; to get the ExtAddr of the SED on the fly. Normally this is very consistent. Is it not the correct API?</span>[/quote] <p>You can use this to get the IEEE 802.15.4 extended address of the device.</p> [quote user=""]2. Under what circumstances would/could the ExtAddr be changed in a SED?[/quote] <p>The 802.15.4 extended address of the device should not change unless you manually change it or erase the network data of the device. Did the device reset right before the address change? It could be that you are not setting the extended address persistent, so it is changed upon reset.</p> [quote user=""]<span>3. Is &#39;</span>otLinkGetFactoryAssignedIeeeEui64 ()<span>&#39; a better way to retrieve&nbsp;the hardcoded MAC?</span>[/quote] <p>This will give you the IEEE EUI-64, which is different from the extended address.</p> <p>Best regards,<br />Marte</p><div style="clear:both;"></div>