Information Technology Reference
In-Depth Information
coni gurations, mismatched MTU coni gurations, and mismatched NIC teaming policies—all of
which are common sources of connectivity issues.
There are a few requirements to using the health check feature that you should know:
◆
As we mentioned earlier, you must be using a version 5.1.0 or version 5.5.0 distributed
switch.
VLAN and MTU checks require at least two NICs with active links.
◆
The teaming policy check requires at least two NICs with active links and at least two
hosts.
◆
By default, vSphere Distributed Switch Health Check is turned off; you must enable it in
order to perform checks.
To enable vSphere Distributed Switch Health Check, perform these steps:
1.
Connect to a vCenter Server instance using the vSphere Web Client.
2.
Navigate to a distributed switch object in the vSphere Web Client, and select the distrib-
uted switch for which you want to enable health checks.
3.
Click the Manage tab, choose Settings, and then select Health Check.
4.
Click the Edit button.
5.
In the Edit Health Check Settings dialog box, you can independently enable checks for
VLAN and MTU, teaming and failover, or both. Click OK when i nished.
Once the health checks are enabled, you can view the health check information on the
Monitor tab of the distributed switch. Figure 5.51 shows the health check information for a dis-
tributed switch once health checks have been enabled.
Closely related to the health check functionality is a feature added in vSphere 5.1 called
vSphere Network Rollback. The idea behind network rollback is to automatically protect envi-
ronments against changes that would disconnect ESXi hosts from vCenter Server by rolling
back changes if they are invalid. For example, changes to the speed or duplex of a physical
NIC, updating teaming and failover policies for a switch that contains the ESXi host's manage-
ment interface, or changing the IP settings of a host's management interface are all examples of
changes that are validated when they occur. If the change would result in a loss of management
connectivity to the host, the change is reverted—or rolled back—automatically.
Rollbacks can occur at two levels: at the host networking level or distributed switch level.
Rollback is enabled by default, but you can enable or disable the feature at the vCenter level
(doing so requires editing the vCenter Server coni guration i le; there is no GUI setting).
In addition to automatic rollbacks, VMware administrators have the option of performing
manual rollbacks. We showed you how to do a manual rollback at the host level earlier in the
section titled “Coni guring Management Networking,” when we discussed the Network Restore
Options area of an ESXi host's DCUI. To perform a manual rollback of a distributed switch, you
use the same process as restoring from a saved coni guration, which is what we're going to dis-
cuss in the next section.
