DNS Resolution for ESXi Hosts
DNS has always been a critical component or VMware server-based virtualization. When an ESX or ESXi cluster came into the mix, its criticality increased exponentially. One of the big differences between and ESX and an ESXi installation is the hostname. ESX will prompt it during the installation, where ESXi does a self-resolution to define its hostname.
Given that ESXi is now confirmed to be the hypervisor of the future, it good times to ensure the basics are in good order.
This is the reason why if an ESXi host boots up and displays "localhost" on the direct console user interface or DCUI (which, by the way is the official name of the yellow and grey screen); that means that the ESXi host as it is cannot resolve its name. There are a few considerations to configuring the host, however. Primarily, how is the host configured with IP addressing and DNS suffixes within the vSphere Client or via a host profile or installation script?
Fig. 1 shows a host that is correctly resolving its IP address to a DNS name in the zone that is configured. The host assigns its addresses via DHCP through a static reservation for the primary MAC address of a virtual switch with two vmnic interfaces assigned to it. Most production environments will not use DHCP, however.
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Figure 1. When a name other than localhost is shown, the ESXi host has correctly resolved its name. (Click image to view larger version.) |
The fact that the hostname can't be specified in the ESXi installation is also confirmed in the vSphere Client (see Fig. 2).
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Figure 2. The vSphere Client doesn't permit for the name of the ESXi host to be changed. Rather the DNS server configuration, which permits hostname resolution. (Click image to view larger version.) |
DNS will continue to be a critical piece of the virtualized infrastructure, yet it is in a way made simpler by ESXi's configuration for the host names.
What tricks have you employed to configure DNS for ESXi hosts? Share your comments here.
Posted by Rick Vanover on 12/07/2010 at 12:48 PM