Windows DNS Queries Failing

I was putting together a PoC late last year and encountered an issue that I’ve not seen before that was caused by some functionality within Windows 2008 that I did not know existed at the time. In fact, no one who I’ve mentioned it to since knew about it either. It seemed sufficiently obscure that I thought I should write about it quickly. In the PoC, I had created a Windows domain based on Server 2008 R2. Setting that up was simple enough and I’d done it many times before. What I began to notice though was that DNS queries forwarded outside of my PoC infrastructure were failing more often than not. This made Microsoft Updates impossible to install amongst other issues. After fiddling with the DNS timeouts and talking with the hosting provider at the remote datacenter to no […]

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Do my ESXi hosts have the same VLANs?

In a small vSphere environment that I’ve recently been working on, I started to notice that some of my VMs were disappearing off the network from time to time. Reboots of the VM didn’t seem to fix the issue but a quick vMotion of the VM to another host did. If you haven’t figured it out yet, one of my hosts was missing a VLAN and VMs connected to a certain portgroup were affected whenever they ran on the host. vSphere will warn you if a host that you’re trying to migrate a VM to doesn’t have the right portgroup and host profiles (if you’re using Enterprise Plus licensing) will alert you to the fact that a portgroup isn’t configured with the right VLAN ID but nowhere in vSphere will you get an alert if a required VLAN is not […]

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Data Rates and P2V

Recently I’ve been working on a project involving some P2V work. Don’t be too surprised – some companies may be 80, 90 or even 100% virtualised already but there are plenty out there that either haven’t started yet or aren’t that far down the road of getting their server estate into a Virtual Infrastructure.

Particularly when it comes to virtualising production servers, the big question that comes up when it comes to arranging downtime for applications / servers and raising change requests is: “How long is it going to take?”


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Creating VLANs in DD-WRT (Part 3)

In the second part of this post I completed the setup of VLANs on my WNR3500L router. To make them available to hosts (and VMs) I now have to configure my Cisco SLM2008 switches. Fortunately that turns out to be fairly simple. The SLM 2008 has a web-based GUI that does the job nicely. Once logged in it’s a matter of opening the VLAN >> VLAN Settings page. Then just tap in the VLAN ID that you want to create and click “Add”. This then drops you into an additional page where you choose which ports to associate the VLAN with. I picked all of the ports on this switch (where my ESX hosts are located). Then I clicked “Save”. It’s just then a case of repeating for the other VLANs that are required. And that’s the switches done. The default configuration […]

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Creating VLANs in DD-WRT (Part 2)

In the first part of this post I created some VLANs on my NetGear WNR3500L router that I’ve flashed with DD-WRT firmware. In this second part of the post I will be assigning IP address ranges to those VLANs and configuring the router’s firewall. I want the VLANs that I setup previously to use separate IP Address ranges. To do this it’s back into to the telnet session and enter the following command: [text]nvram set rc_startup=’ #!/bin/ash PATH="/sbin:/usr/sbin:/bin:/usr/bin:${PATH}" ifconfig vlan6 netmask ifconfig vlan7 netmask ifconfig vlan8 netmask ifconfig vlan9 netmask ifconfig vlan10 netmask ifconfig vlan11 netmask ifconfig vlan12 netmask ifconfig vlan13 netmask ifconfig vlan14 netmask ifconfig vlan15 netmask ifconfig vlan6 up ifconfig vlan7 up ifconfig vlan8 up ifconfig vlan9 up […]

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