Tag Archives: Troubleshooting

Ping from specific VMkernel adapter in vSphere 6

When troubleshooting network problems on ESXi hosts you want to specify the outgoing VMkernel adapter. As explained here you can ping from a specific VMkernel adapter with the -I parameter. In vSphere 6.0, or with VXLAN activated, this might not work as expected and displays the following error.

[root@esx:~] ping -I vmk1
Unknown interface ‘vmk1’: Invalid argument

The problem is related to the multiple TCP/IP Stack features introduced in vSphere 6.0. To ping from specific VMkernel adapters that are not in the default Stack (defaultTcpipStack) you have to manually specify the NetStack with the -S parameter.

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How long are Virtual Machines stunned for Snapshots and vMotion?

I’ve read this excellent article by Cormac Hogan explaining why and when a Virtual Machine receives a “stun”. This post is a follow-up explaining how you can determine the duration of a Virtual Machine stun on the most common vSphere functions:

  • Create a Snapshot
  • Delete a Snapshot
  • vMotion

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What’s Inside an ESXi vm-support Bundle?

When you open a Support Request (SR) at VMware, the Global Support Services usually requests you to collect diagnostic information. You can create this log bundle with a special command line tool (vm-support), with the vSphere (Web-)Client or with the API. No matter how you create the bundle the result is always the same: a .tgz file containing your ESXi Host name and the creation date with a size of about 30 – 300MB.

This post explains what’s inside this log bundle, but instead of simply extracting the file and looking at the result, I am going to take a look on how the file is created and what’s part of the process.

Why is it important to know? Because it does not only contain data that allows VMware GSS to identify your issue, but also to help yourself to enhance your troubleshooting skills. The script gathers the output of many useful commands and there is nearly no black magic involved. You do not need special tools or internal VMware knowledge to make use of this log bundle.


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ESXi Network Troubleshooting with tcpdump-uw and pktcap-uw

This post explains how you can troubleshoot network problems by capturing network traces of ESXi host by using the tcpdump-uw and pktcap-uw utility. The pktcap-uw tool is an enhanced packet capture and analysis tool that can be used in place of the legacy tcpdump-uw tool. The pktcap-uw tool is included by default in ESXi 5.5 and later. This post explains the main differences of both tools and how to use them.

tcpdump-uw vs. pktcap-uw – It’s not the same!


Capabilities of tcpdump-uw and pktcap-uw

The tcpdump-uw utility captures traffic from VMkernel adapters. The pktcap-uw utility, introduced in ESXi 5.5 can capture traffic that flows through physical network adapters, VMkernel adapters, and virtual machines adapters.

But it’s more complex…

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ESXi 5 Network Troubleshooting Commands

Check if a remote host is online and reachable.

~ # ping
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=58 time=13.701 ms
64 bytes from icmp_seq=1 ttl=58 time=10.176 ms
64 bytes from icmp_seq=2 ttl=58 time=9.055 ms

--- ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 9.055/10.977/13.701 ms

Ping from a specific VMkernel adapter.

~ # ping -I vmk1
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=58 time=9.991 ms
64 bytes from icmp_seq=1 ttl=58 time=9.270 ms

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Howto Shrink a Thin Provisioned Virtual Disk (VMDK)

Thin provisioned disks are a great feature to save capacity as you virtual machines filesystem will never use the full capacity. I do not know a single system where you do not have at least 10GB of free space for OS disks. I am not considering databases, applications or fileservers which will grow constantly. Having thin provisioned disk is usually no longer a performance problem so it is a valid design choice even in production.

A common issue with thin disks is that the size will grow when required, but never shrink. When you require the capacity only once you might want to get it back from the virtual machine. This post describes how to reclaim unused space from the virtual machine.

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Identify Disk Usage of a Thin Provisioned Virtual Disk

This post demonstrates various ways to identify the disk usage of a thin provisioned virtual disk.

I have a virtual machine with a 10 GB thin provisioned disk. You can verify the disk type from the virtual machine settings page.


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Enabling verbose logging on QLogic and Emulex HBAs in ESXi 5.5

KB1005576 explains how to enable or disable verbose logging on QLogic and Emulex Host Bus Adapters. With ESXi 5.5 and its Native Device Driver Architecture the option has been slightly changed, but is still available. This post explains how to enable verbose logging on QLogic and Emulex HBAs in ESXi 5.5.

The new native drivers and their predecessor are:

Emulex FC: lpfc (replaces lpfc820)
QLogic FC: qlnativefc (replaces qla2xxx)

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vSphere Mobile Watchlist – VM Administration for Andorid and iOS

VMware has just published a new App for Andorid and iOS: vSphere Mobile Watchlist. The App which has been announced at the last VMware Partner Exchange 2014 allows to monitor your virtual machines in your vSphere infrastructure remotely on your phone. I’ve tested the app on my HTC One to see how powerful it is.


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Howto Check Network Port Availability from vMA

VMwares vSphere Management Assistant does not have much tools available. When you vMA is behind a firewall you might want to check if ports are reachable for troubleshooting purposes. As the vMA does not come with telnet or netcat you can use the built in bash feature:

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