Just some stuff I discovered today …<\/p>\n
Azure Virtual Networks contain address spaces<\/em> (e.g. Within a Virtual Network you create subnets<\/em>. I thought you had to necessarily create subnets, but turns out they are optional. If you don’t want to create subnets just create a default one that encompasses the entire address space.<\/p>\n VMs in Azure are automatically assigned IP addresses. That is to say there’s a DHCP server running in Azure, and depending on which subnet your VM is connected to the DHCP server allocates it an\u00a0IP address. (You can tell the DHCP server to always assign the same IP address to your VM – I discussed\u00a0that in an earlier post<\/a>). Remember though, that a DHCP server gives clients more than just an IP address. For instance it also tells clients of the DNS servers. Azure lets you specify up to 12 DNS servers to be handed out via DHCP. But there’s a catch though, and that’s the thing\u00a0I learnt today – the DNS servers you specify are per<\/em> Virtual Network, not per subnet (as I was expecting). So if your Virtual Network has multiple subnets and you would like to specify different DNS servers for each of these subnets, there’s no way to do it!\u00a0<\/p>\n So, lessons learnt today:<\/p>\n I am not going to change my network config now – it’s just a test environment after all and I don’t mind if clients pick up\u00a0a DNS server from a different subnet, plus it’s such a hassle changing my Virtual Network names and pointing VMs to these!\u00a0– but the above\u00a0is worth remembering for the future.\u00a0Virtual Networks are equivalent to the\u00a0networks one typically uses; Subnets are optional and better to use them only if you want to classify things separately.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":" Just some stuff I discovered today … Azure Virtual Networks contain address spaces (e.g. 192.168.0.0\/16). I was under the impression a Virtual Network can contain only one address space, but that turned out to be incorrect. A Virtual Network can contain multiple address spaces (e.g. 192.168.0.0\/16 and 10.10.0.0\/24\u00a0– notice they have no relation to each … Continue reading Notes on Azure Virtual Networks, subnets, and DNS<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false}}},"categories":[333,183],"tags":[383],"jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/posts\/2076"}],"collection":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/comments?post=2076"}],"version-history":[{"count":0,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/posts\/2076\/revisions"}],"wp:attachment":[{"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/media?parent=2076"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/categories?post=2076"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rakhesh.com\/wp-json\/wp\/v2\/tags?post=2076"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}192.168.0.0\/16<\/code>). I was under the impression a Virtual Network can contain only one address space, but that turned out to be incorrect. A Virtual Network can contain multiple address spaces (e.g. 192.168.0.0\/16<\/code> and<\/em> 10.10.0.0\/24<\/code>\u00a0– notice they have no relation to each other). A\u00a0Virtual Network is just a logical way of saying all these address spaces belong to\u00a0the same network. A\u00a0Virtual Network is also the entity which has a gateway and to which\u00a0you can connect your Physical Network.\u00a0<\/p>\n\n
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192.168.1.0\/24<\/code>. If I have just one subnet in this space (a subnet\u00a0192.168.1.0\/24<\/code>) then all my servers\u00a0will get random IPs from 192.168.1.4<\/code> onwards. But maybe I don’t want that.<\/li>\n192.168.1.4 - 192.168.1.10<\/code>), while all my DNS servers get from a different chunk (192.168.1.11 - 192.168.11.16<\/code>).\u00a0<\/li>\n\/29<\/code>\u00a0– i.e.\u00a0a subnet of 8 hosts, of which 3 are reserved, so effectively a subnet of 5 hosts – and connect VMs to the these subnets. As far as VMs in each subnet are concerned they are in different networks (because the IP address\u00a0class will be that of the subnet) but for all other intents and purposes they are on the same network. And from a DHCP point of view all subnets on the same Virtual Network will get the same settings. (Note to self: if\u00a0the VMs are in a domain,\u00a0remember to add these multiple subnets to the same site so DC lookup works as expected).<\/li>\n