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How to clear the ARP cache in ESXi prior to vSphere 5.5

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Yesterday, I wrote an article about a new ESXCLI command that will be available as part of the soon to be released vSphere 5.5 release which allows a user to clear the ARP cache on an ESXi 5.5 host. It was my understanding that with past releases of ESXi, that it is not possible to clear the ARP cache. While working on that article, I came across an internal thread and learned that it was possible to clear ARP entries prior to ESXi 5.5, however the method is not as ideal as using the new ESXCLI command.

Disclaimer: This is not officially supported by VMware, please use at your own risk

In ESXi 5.1, you can list the current ARP entries for an ESXi host by running the following ESXCLI command:

esxcli network ip neighbor list

To clear a particular ARP entry, you will need to use the unsupported vsish interface. To delete a specific ARP entry, you will need to run the following command:

vsish -e set /net/tcpip/v4/neighbor del [IP-ADDRESS]

Here is a screenshot of listing the current ARP entries using ESXCLI and then deleting one of entries using vsish:

As mentioned in my previous article, I am glad we have made this into an official command in ESXCLI 5.5, but if you are in a crunch you can still clear an ARP entry if you are not running ESXi 5.5 using vsish.

How to clear the ARP cache on ESXi using new ESXCLI 5.5

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The ability to clear the ARP cache/table for an ESXi host is feature that has been requested from customers from time to time and usually for diagnosing network related issues. In previous releases, this was not something you could easily do and it was nice to see this feature get implemented in a new ESXCLI command that will be available as part of the vSphere 5.5 release.

The ESXCLI "network ip neighbor" namespace has been enhanced to include a new option:

You can list ARP table entries using the "list" operation and you can now clear a specific ARP entry using the "remove" operation.

To clear an ARP entry, you will need to specify the IP Address you wish to clear, the IP protocol whether it is IPv4 or IPv6 and you also have the option to specify the particular VMkernel interface. If you do not specify the particular VMKernel interface, then the entry will be removed for all interfaces.

Here is a screenshot of listing of the current ARP entries and then removing an entry for VMkernel interface 1:

This will definitely be a useful ESXCLI command to be aware of the next time you need to troubleshoot a network issue!

Note: I mentioned earlier that clearing the ARP cache was not something that you could do prior to vSphere 5.5. However, while working on this article, I actually learned it was possible to clear the ARP cache, but it was not very user friendly like the new ESXCLI 5.5 command. In a separate article, I will show you how can clear the ARP cache on earlier versions of ESXi.

If you wish to clear the ARP cache on an ESXi host prior to ESXi 5.5, please take a look at this article for more details.

How to bootstrap vCenter Server onto a single VSAN node Part 2?

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In this article, I will provide a step by step walk through on how to setup and configure single VSAN node that will allow you to deploy a vCenter Server onto a VSAN datastore. This initial "bootstrapping" can help when initially building out your VSAN cluster and can come in handy for greenfield deployments and potentially for brownfield deployments as well. Before getting started, make sure you have taken a look at How to bootstrap vCenter Server onto a single VSAN node Part 1.

Environment:

  • 3 physical host
  • Each host as a small iSCSI boot LUN for ESXi installation (this can be another local disk or USB/SD card)
  • Each host has single SSD and SATA disk (minimum)

Step 1 -  Install ESXi 5.5 onto your physical hosts, we technically only need one host to begin the process but you will probably want to have two additional hosts ready unless you do not care about your vCenter Server being able to recover if there is any hardware issues.

Step 2 - You will need to modify the default VSAN storage policy on the ESXi host in which you plan to provision your vCenter Server. It looks like this behavior changed during the VSAN beta and when VSAN was GA'ed yesterday with vSphere 5.5 Update 1. You will need to run the following two ESXCLI commands to enable "force provisioning":

esxcli vsan policy setdefault -c vdisk -p "((\"hostFailuresToTolerate\" i1) (\"forceProvisioning\" i1))"
esxcli vsan policy setdefault -c vmnamespace -p "((\"hostFailuresToTolerate\" i1) (\"forceProvisioning\" i1))"

You can confirm you have the correct VSAN default policy by running the following ESXCLI command:

~ # esxcli vsan policy getdefault
Policy Class  Policy Value
------------  --------------------------------------------------------
cluster       (("hostFailuresToTolerate" i1))
vdisk         (("hostFailuresToTolerate" i1) ("forceProvisioning" i1))
vmnamespace   (("hostFailuresToTolerate" i1) ("forceProvisioning" i1))
vmswap        (("hostFailuresToTolerate" i1) ("forceProvisioning" i1))

We start off with our first ESXi host and as you can see from the screenshot below, we do not have additional datastores that we can use to provision our vCenter Server.

Step 3 - You will need to identify the disks that you will be using on the first ESXi host to contribute to the VSAN datastore. You can do so by running the following ESXCLI command:

esxcli storage core device list

To get specific details on a particular device such as identifying whether it is an SSD or regular HDD, you can specify the -d option and the device name.

Once you have identified the disks you will be using, make a note of the the disks names as they will be needed in the upcoming steps. As mentioned in my environment, I only have a single SSD and single HDD and their respective device names are naa.50026b72270126ff & naa.5000c500331bca77

Step 4 - Before we can create our VSAN datastore, we need to first create a VSAN cluster. One of the parameters that is needed when going through this "bootstrapping" method without a vCenter Server is a unique UUID to identify the VSAN cluster. The UUID is in the format of "nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn" where n is a hexidecimal value. You can easily generate one within the ESXi Shell by leveraging the following Python snippet

python -c 'import uuid; print(str(uuid.uuid4()));'

Step 5 - To create a VSAN cluster, we will use the following ESXCLI command and specify the UUID from the previous step for the -u option:

esxcli vsan cluster join -u UUID

UPDATE (02/11/15) - In vSphere 6, you no longer have to perform step 4 to generate a UUID. There is now a new ESXCLI command which will automatically create a VSAN Cluster and generate a UUID automatically by running the following command:

esxcli vsan cluster new

Once the VSAN cluster has been created, you can retrieve information about the VSAN cluster by running the following ESXCLI command:

esxcli vsan cluster get

Step 6 - Next we need to add the disks from our ESXi host to create our single node VSAN datsatore. To do so, we will need the disk device names from our earlier step for both SSD and HDDs and run the following ESXCLI command:

esxcli vsan storage add -s SSD-DISK-ID -d HDD-DISK-ID

The -d option specifies regular HDD disks and the -s option specifies an SSD disk. If you have more than one HDD disk, you will need to specify multiple -d entries. You can also take a look at the disks being contributed to the VSAN datatore by running the following ESXCLI command:

esxcli vsan storage list

Step 7 - To save us one additional step, you can also enable the VSAN traffic type on the first ESXi host using ESXCLI and you can also do this for the other two hosts in advance. This step does not necessary have to be done now as it can be done later when the vCenter Server is available and using the vSphere Web Client. You will need to either create or select an existing VMkernel interface to enable the VSAN traffic type and you can do so by running the following ESXCLI command:

esxcli vsan network ipv4 add -i VMK-INT

At this point, you now have a valid VSAN datastore for your single ESXi host! You can verify this by logging into the vSphere C# Client and you should see the VSAN datastore mounted to your ESXi host.

At this point, you are now ready to deploy your vCenter Server 5.5 onto the VSAN datastore. The next series of steps outline the deployment of the VCSA for completeness of the article.

Step 8 - Deploy the VCSA 5.5 OVA/OVF onto the VSAN datastore and power on the VM.

UPDATE: You skip Steps 9-11 by leveraging ovftool 4.0 to inject the required OVF properties when deploying the VCSA, take a look at this article for more details.

Step 9 - Since you can not configure the OVF properties for the VCSA, you will notice that networking is not configured (unless you happen to have DHCP on the network). If you are like most Enterprise customers, you will not have DHCP running in your environment and you will need to configure a static IP.

Step 10 - Login to the VCSA console and we will use the following VAMI CLI /opt/vmware/share/vami/vami_set_network to configure the IP Address for the VCSA. Here is an example of what that command would look like:

/opt/vmware/share/vami/vami_set_network eth0 STATICV4 172.24.68.14 255.255.255.0 172.24.68.1

For more details on the syntax, you can refer to this blog article here. At this point, you should be able to ping your VCSA and verify connectivity.

Step 11 (Optional) - In addition to IP connectivity, you may also want to configure your DNS Server and DNS search domain before configure the VCSA application. You can also do this by using the following VAMI CLI /opt/vmware/share/vami/vami_set_dns and for search domain, you would need to add the entry to /etc/resolve.conf

Step 12 - You now are ready to configure the VCSA. Open a browser and connect to https://[VCSA-IP]:5480 and proceed through the VCSA setup wizard.

Step 13 - Once the VCSA has been configured, you can now login to the vSphere Web Client and create a Datacenter object and then a vSphere Cluster and enable VSAN. Make sure you also enter your VSAN beta license key under the "Manage" section of the vSphere Cluster before you can use VSAN.

Step 14 - Add all three of your ESXi hosts to the vSphere Cluster. If you recall earlier we had enabled the VSAN traffic type on our first ESXi host and if you did not run the command on the remainder ESXi hosts, you will need to do so using the vSphere Web Client under the "Networking" section of each ESXi host

Step 15 - Once all three ESXi hosts have been added to the vSphere Cluster, we should now see their local storage contributed to the VSAN datastore under the "General" tab

Step 16 (Optional) - If for whatever reason the disks do not get automatically claimed, you can click on "Disk Management" and manually claim them. If you selected "Automatic" mode when enabling VSAN, the disks on each ESXi host should automatically be handled by VSAN. However, they may not be claimed if the disks are being seen as "remote" versus "local" devices.

Step 17 - The final thing I would recommend is to configure the VCSA to automatically startup and shutdown when the ESXi host reboots. To do so, login to the ESXi host using the vSphere C# Client and click on "Virtual Machine Startup/Shutdown" under the Configuration tab.

So there you have it! You are now running the vCenter Server on top of the VSAN datastore without having to initially setup a local VMFS or rely on an external NFS volume to deploy your vCenter Server and build up to the full VSAN cluster. By leveraging this bootstrap method, you can easily standup a fully self contained storage and compute cluster which is ideal for an SMB or ROBO environment. The best part of about this setup is that the VCSA will use the default VSAN storage policy which is to tolerate at least one failure and as you add your 2nd and 3rd ESXi host, you will automatically have resiliency for the VCSA.