{"id":827,"date":"2026-02-26T10:12:03","date_gmt":"2026-02-26T10:12:03","guid":{"rendered":"https:\/\/networkingnotebook.com\/?p=827"},"modified":"2026-02-26T10:20:47","modified_gmt":"2026-02-26T10:20:47","slug":"eui-64","status":"publish","type":"post","link":"https:\/\/networkingnotebook.com\/?p=827","title":{"rendered":"EUI-64"},"content":{"rendered":"\n<p><br>Today I am going to talk about EUI-64 (Extended Unique Identifier 64-bit). IPv6 is a little different from IPv4 because not only does it have DHCPv6, it also has a feature called SLAAC (Stateless Address Autoconfiguration) which can use EUI-64. SLAAC is used to automatically generate an IPv6 address, and EUI-64 is used to automatically generate the interface ID portion with only the device&#8217;s MAC address. It does this in 3 simple steps:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>It divides a MAC address in half, 24 bits for each half.\u00a0<\/li>\n\n\n\n<li>It inserts a 16 bit hexadecimal of FFFE after the first 24 bits, between the two halves.\u00a0<\/li>\n\n\n\n<li>It then flips the 7th binary bit (U\/L bit) of the first byte.<\/li>\n<\/ol>\n\n\n\n<p>Once these steps are done, the interface ID has been made and the device interface now has an automatically assigned IPv6 address.&nbsp; An example would be this below:&nbsp;<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"451\" src=\"https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-57-1024x451.png\" alt=\"\" class=\"wp-image-829\" srcset=\"https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-57-1024x451.png 1024w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-57-300x132.png 300w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-57-768x338.png 768w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-57-1536x676.png 1536w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-57-2048x902.png 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p>The seventh bit that is being inverted is called a \u201cU\/L bit.\u201d This bit is used to determine how a MAC address was assigned. There are only two ways a MAC address can be assigned either universally by the manufacturer (Burned In Address) or locally by an IT member. When the 7th bit of the first byte of the MAC address is 0, that means the address was universally administered by the manufacturer (BIA) and is globally unique. When the 7th bit is 1, that means the MAC address has been locally assigned by a human, most likely an IT member.&nbsp;<\/p>\n\n\n\n<p>In this example the first 8 bits are 00 equaling to binary of 0000 0000. When you invert the U\/L bit, it will turn to 0000 0010 which turns to a decimal of 02 instead of 00.&nbsp;<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"662\" src=\"https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-60-1024x662.png\" alt=\"\" class=\"wp-image-834\" srcset=\"https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-60-1024x662.png 1024w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-60-300x194.png 300w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-60-768x496.png 768w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-60-1536x993.png 1536w, https:\/\/networkingnotebook.com\/wp-content\/uploads\/2026\/02\/image-60-2048x1324.png 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Today I am going to talk about EUI-64 (Extended Unique Identifier 64-bit). IPv6 is a little different from IPv4 because not only does it have DHCPv6, it also has a feature called SLAAC (Stateless Address Autoconfiguration) which can use EUI-64. SLAAC is used to automatically generate an IPv6 address, and EUI-64 is used to automatically&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-827","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=\/wp\/v2\/posts\/827","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=827"}],"version-history":[{"count":3,"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=\/wp\/v2\/posts\/827\/revisions"}],"predecessor-version":[{"id":835,"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=\/wp\/v2\/posts\/827\/revisions\/835"}],"wp:attachment":[{"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=827"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=827"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/networkingnotebook.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=827"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}