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I want to ensure that my AWS EC2 instance has a static MAC address (for an app that ties the license to the MAC address). From what I read I just need to add an ENI to the instance to get a static MAC.

However, from the AWS console | Network & Security | Network Interfaces, I see my first NIC has an eni-XXXXX identifier. Does that mean that even the default NIC assigned to my instance will keep it's MAC address between stop/starts?

So is every NIC an ENI? (with static MAC) If so why does the Amazon site say to add an ENI? Or is the first NIC not really an ENI, but the second one is?

Later postings (on the AWS forums) suggest that if you assign an EIP to an ENI then the MAC address will survive start/stops. Is this correct?

Lots of contradicting information

TSG
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  • *"why do the docs says to add an ENI"* Where do they say this? (Also, why do you particularly need a static MAC? It sounds like you might be doing something the hard way.) – Michael - sqlbot Apr 06 '19 at 03:29
  • I m not aware of any relationship between MAC address and Eni, but Eni have been introduced when AWS put virtual networking into hardware. I believe that happened in c5, m5 instances end of 2017 and is also present in t3, r5 instances. Any newer instance on the nitro architecture will have an Eni by default and there is usually no reason to build anything new on older instances unless you are looking to use spot instances – jdog Apr 06 '19 at 06:35
  • My understanding is an ENI gives you a static MAC address. – Tim Apr 06 '19 at 09:17
  • check this https://stackoverflow.com/questions/5435642/fixed-mac-addresses-on-windows-ec2-machines – Elshan Dec 20 '21 at 04:25

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