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Can not ping with vm name RRS feed

  • Question

  • I have a vm which have a external network with DHCP enabled, then I change the setting of vm network, change the external network to internal network.
    i use the hyper-v host machine to ping the vm name, always got the old IP address and can not success. What should I do in this condition ? Seems DHCP server have remember the old IP, and I have no change to change it.
    Wednesday, December 24, 2008 9:29 AM

Answers

  • Hi,

     

    According to your description, it seems to be a DNS registration or cache issue. To troubleshoot this problem efficiently, please perform the following steps to see if the issue remains:

     

    Step 1: Re-register A record for the new IP address

    ---------------------------------------------------------------

    I understand that you have run the “ipconfig /registerdns” command on the guest machine. Here I would like to confirm where the DNS server that the host machine uses locates. If it is on the external network, the guest in the “Internal” network cannot access computers in the host network. The “ipconfig /regsiterdns” command cannot register DNS name dynamically. You will need to update the A record on the DNS server manually.

     

    After you ensure that the DNS server contains  the correct A record that points to the new IP address, please perform the following steps to clear DNS cache on the DNS server:

     

    -          Open the DNS snap-in.

    -          Right click your server item, and click "Clear Cache".

     

    Step 2 : Clear cache on host

    ---------------------------------------------------------------

    On the host machine, navigate to the elevated command prompt, run the following commands:

     

    Flush the NetBIOS name cache:                nbtstat -R

    NetBIOS name update:                            nbtstat -RR

    Flush DNS cache:                                   ipconfig /flushdns

     

    Please test this problem again.

     

    Best Regards,

    Vincent Hu

    • Marked as answer by Vincent Hu Friday, January 2, 2009 1:03 AM
    Monday, December 29, 2008 10:58 AM

All replies

  •    It is probably DNS not DHCP which is remembering the old IP linked to the machine name.

       Is there a DHCP server on the internal network? If not you will need to configure the new address manually. How you get the new address into DNS depends on how your network is configured.

        This really has nothing to do with Hyper-V. You would have the same problem if you unplugged a machine from one physical network and plugged it into a different one.
    Bill
    Wednesday, December 24, 2008 11:01 AM
  • I only use hyper-v created an internal network and do nothing. There's another scenario, I use internal network to get an IP address dyanmically, then I change it to a static IP. When I use the host to ping this vm name, still can not ping through, use the changed Ip is ok.
    In the host machine, I use nslookup, the vm's IP is still the old one. Then in the vm I try to use ipconfig /registerdns and wait a long time. Let the host flushdns, ping again, still the same problem. I do not have DNS in the internal network.
    Thursday, December 25, 2008 1:57 AM
  • Hi,

     

    According to your description, it seems to be a DNS registration or cache issue. To troubleshoot this problem efficiently, please perform the following steps to see if the issue remains:

     

    Step 1: Re-register A record for the new IP address

    ---------------------------------------------------------------

    I understand that you have run the “ipconfig /registerdns” command on the guest machine. Here I would like to confirm where the DNS server that the host machine uses locates. If it is on the external network, the guest in the “Internal” network cannot access computers in the host network. The “ipconfig /regsiterdns” command cannot register DNS name dynamically. You will need to update the A record on the DNS server manually.

     

    After you ensure that the DNS server contains  the correct A record that points to the new IP address, please perform the following steps to clear DNS cache on the DNS server:

     

    -          Open the DNS snap-in.

    -          Right click your server item, and click "Clear Cache".

     

    Step 2 : Clear cache on host

    ---------------------------------------------------------------

    On the host machine, navigate to the elevated command prompt, run the following commands:

     

    Flush the NetBIOS name cache:                nbtstat -R

    NetBIOS name update:                            nbtstat -RR

    Flush DNS cache:                                   ipconfig /flushdns

     

    Please test this problem again.

     

    Best Regards,

    Vincent Hu

    • Marked as answer by Vincent Hu Friday, January 2, 2009 1:03 AM
    Monday, December 29, 2008 10:58 AM
  • It works, Thanks!
    Friday, January 23, 2009 7:06 AM