Tag Archives: network

Unable to connect virtual NIC in vCloud Air DRaaS

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I had a customer open a service request, they were in the middle of a DR test using vCloud Air DRaaS and were unable to connect 1 virtual machine to the network. It kept erroring out with a generic unable to connect error.

It turns out that their VM had a VMDK sized with a decimal point, like 50.21GB instead of just 50GB. I don’t see it often, but this sometimes happens when P2V a machine. The vCloud Director backend can’t handle the decimal point in the disk size, so it errors out.

I’m not entirely sure why the error happens, but the fix is to resize your source disk to a non-decimal number and run replication again.

APC PDU configuration trick

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I was trying to configure an APC7811 PDU, which has a network port for remote access. It’s a metered PDU so you can log in remotely and look at power consumption.

I’d never had to configure one before so I just popped in the CD that came with it and tried to configure an IP address by using the discovery tool. Regardless of which IP address I tried, I kept getting “The IP is already in use on the network.”

This configuration method is in the documentation, but it’s buried at the end… I think I’ll use this every time now as it’s fast and doesn’t require the vendor’s CD.

The MAC address is on the back of the PDU and on the Quality Assurance slip included in the package.

  1. Use ARP to define an IP address for the PDU,
    and use the PDU’s MAC address in the ARP
    command. For example, to define an IP
    address of 156.205.14.141 for the PDU that has
    a MAC address of 00 c0 b7 63 9f 67, use one
    of the following commands:

    Windows command format:
    arp -s 156.205.14.141 00-c0-b7-63-9f-67

    LINUX command format:
    arp -s 156.205.14.141 00:c0:b7:63:9f:67

  2. Use Ping with a size of 113 bytes to assign the
    IP address defined by the ARP command. For
    example:

    Windows command format:
    ping 156.205.14.141 -l 113

    LINUX command format:
    ping 156.205.14.141 -s 113

  3. Use Telnet to access the PDU at its newly
    assigned IP address. For example:

    telnet 156.205.14.141

  4. Use apc for both user name and password.

At this point the IP address is configured for the interface, you can browse to the IP via HTTP. Don’t forget to delete your static ARP entry.

Kernel Handles and Network Disconnects

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We’ve had recurring problems recently with a file server mysteriously losing connection to the network for a few seconds. After going through all of the usual hardware checks, NIC, switch, drivers, etc, we came across this Microsoft NT Debugging Blog entry on kernel file handles. It essentially says to check running processes via Task Manager, Select Columns and add the “Handle Count” column, then sort by it. Anything over 5,000 handles is something to question. We found a process with over 350,000 handles causing our timeout issues. Filed a bug report with the application vendor and the problem disappeared.