{"id":978,"date":"2016-04-08T06:20:43","date_gmt":"2016-04-08T06:20:43","guid":{"rendered":"https:\/\/fir3netwp.gmsrrpobkbd.com\/2016\/04\/08\/stretched-l2-domains-vmotion\/"},"modified":"2021-07-27T19:59:57","modified_gmt":"2021-07-27T19:59:57","slug":"stretched-l2-domains-vmotion","status":"publish","type":"post","link":"https:\/\/www.fir3net.com\/Networking\/Terms-and-Concepts\/stretched-l2-domains-vmotion.html","title":{"rendered":"Stretched L2 Domains + VMotion"},"content":{"rendered":"<h2><strong>Issues with Layer2 across DCs<\/strong><\/h2>\n<ol>\n<li>Ideally, data centers do not share fate. But extending L2 creates a common broadcast domain in 2 data center. Now, we are sharing fate<\/li>\n<li>Traffic patterns become sub-optimal\n<ul>\n<li>Where does the default-gateway live? In the local DC? Or remote?<\/li>\n<li>Traffic to load balancer to pool member, but pool member lives in the remote DC now<\/li>\n<li>And that&#8217;s just L3 considerations. What about L2? How is spanning tree handled between DCs?<\/li>\n<li>Dealing with these issues has spawned whole new protocols, including Overlay Transport Virtualization (OTV) from Cisco that isolates protocols like STP, HSRP, and VTP to attempt to isolate failure domains and avoid FHRP-related traffic tromboning<\/li>\n<\/ul>\n<\/li>\n<li>Redundant links between DCs becomes even more critical, because there&#8217;s an application assumption that the network is always available<\/li>\n<li>Latency tends to be high and bandwidth tends to be constrained in DCI, which make it hard to successfully vMotion anything. vMotions are huge datasets constantly changing<\/li>\n<li>Problems you&#8217;d have anyway that are bandwidth problems of their own&#8230;\n<ul>\n<li>How is storage being synced between sites?<\/li>\n<li>What about database stores?<\/li>\n<\/ul>\n<\/li>\n<li>Site awareness\n<ul>\n<li>How do you abstract the current site of a workload so that the compute knows where it&#8217;s running?<\/li>\n<li>Sync storage across sites \u2013 active\/active<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p><a href=\"https:\/\/packetpushers.net\/podcast\/podcasts\/datanauts-029-evil-behind-long-distance-vmotion-stretched-l2\/\" class=\"broken_link\">https:\/\/packetpushers.net\/podcast\/podcasts\/datanauts-029-evil-behind-long-distance-vmotion-stretched-l2\/<\/a><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Issues with Layer2 across DCs Ideally, data centers do not share fate. But extending L2 creates a common broadcast domain in 2 data center. Now, we are sharing fate Traffic patterns become sub-optimal Where does the default-gateway live? In the local DC? Or remote? Traffic to load balancer to pool member, but pool member lives &#8230; <a title=\"Stretched L2 Domains + VMotion\" class=\"read-more\" href=\"https:\/\/www.fir3net.com\/Networking\/Terms-and-Concepts\/stretched-l2-domains-vmotion.html\" aria-label=\"Read more about Stretched L2 Domains + VMotion\">Read more<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Stretched L2 Domains + VMotion - Fir3net<\/title>\n<meta name=\"description\" content=\"Issues with Layer2 across DCs Ideally, data centers do not share fate. But extending L2 creates a common broadcast domain in 2 data center. Now, we are\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.fir3net.com\/Networking\/Terms-and-Concepts\/stretched-l2-domains-vmotion.html\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Stretched L2 Domains + VMotion - Fir3net\" \/>\n<meta property=\"og:description\" content=\"Issues with Layer2 across DCs Ideally, data centers do not share fate. But extending L2 creates a common broadcast domain in 2 data center. 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