Virtual PC, Shared Networking and the problems with Ping

Virtual PC, Shared Networking and the problems with Ping

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Anyone who has spent time troubleshooting networking problems will be more than familiar with the tool - Ping. However - there are two problems with using ping with shared networking under Virtual PC:

  1. 192.168.131.254 does not respond to a ping.

    One of the first steps in network troubleshooting is to try and ping your gateway address.  Unfortunately, with Virtual PC and shared networking, the gateway address (192.168.131.254) does not respond to a ping.  This is completely benign behavior - as all other aspects of networking still work - however it has tripped up many people who were trying to diagnose network connectivity with shared networking.

  2. You can only ping external computers if you are running Virtual PC with an administrative user account.

    Virtual PC's shared networking implementation is a simple NAT engine.  Virtual PC is responsible for sending and receiving network traffic for the virtual machine as a standard Windows user mode application.  For security reasons, only applications that are running as an administrative user are able to generate translated ICMP packets, such as the ones that are needed to support ping with shared networking.

    N.B. This means that if you are running on Vista and want to use ping inside a virtual machine with shared networking, you will need to manually launch Virtual PC 'as administrator'.

Thankfully neither of these issues are show stopping problems, but are just interesting oddities.

Cheers,
Ben

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  • Hi,

    I have been working for the last two months with Virtual PC R2 under Vista on my Dell Inspiron laptop.

    For the NAT thing, If I want to ping the host OS and any of the other VMs, I create always two virtual NICs, one to the Microsoft Loopback and another using NAT. But you have to disable the Loopback if you want to access the outside network.

    My problem right now is that whenever I hibernate the laptop (just closing the laptop or selecting hibernating) the microsoft loopback hangs and I have to reboot the host machine to make it to work it again. It is annoying, since I am using a Windows machine for developing against another machine, and I keep different connections opened and I want to keep the system in the same state as I left it and be able to keep on working where I left the system.

    I have tried to disable/enable the loopback adapters (from the host or the guest machine) and even try to pause the VM. Nothing works.

    If someone could help me out, I would be grateful

    Miguel

  • Miguel -

    I have not seen this behavior, and do not know what could be causing the problem you are seeing.  I would recommend that you contact Microsoft Product Support for help.

    Cheers,

    Ben

  • Hi

    I have a different problem. I need to set up a testbed which has following topology:

    A-----B--Corporate Network--C----D

    A talks to B only and D talks to C only. I have two physical machines (H1 and H2), with Vista running on them. I have installed Virtual PC on H1 and H2, and installed two virtual machines on each of them. A and B are running on H1 and similarly C and D are running on H2. All the virtual machines have vista installed on them, and machines B and C have 2 NIC cards each. Due to policy of corporate network i cannot share the internet connection on my host machines and hence i'm not able to setup them as a NAT server. I tried giving A and 1 of the NIC card of the B as private IP address and using the other NIC card to talk to corpnet. And, I also enabled machines B and C as routers and added routes in their routing table. But the machines A and B (similarly C and D) are not able to talk to each other.

    Can any one tell me what have I done wrong or how shall i go about setting up this topology using virtual pc?

    Thanks in advance.

    Manveer

  • There are cases where the inability to ping can be a show stopper - at least without rewriting some code.  I have a remote server maintenance toolkit that, just to make sure the server is alive, pings selected servers from a web service and returns the results to the server tech.  Not that I foresee it going to a virtual server any time soon but since we are virtualizing heavily so it could happen.  This app obviously won't be a good candidate for virtualization unless I replace the ping with an RPC call or other means of checking for a heartbeat.

  • Hello, I am having trouble setting up the networking in MS virtual Machine 2007

    In many places I have seen refrence to "loopback' or NAT, or "switch"

    In my options I have NAT but no switch or loopback.

    I have installed ubuntu linux as a web host test bed for testing php scripts before I upload to my live server.

    I can not ssh into the virtual machine as the network is not configured properly.

    Can you help?

  • Hello there dear Ben,

    I hope you will have the time to respond this email since I am struggling with this issue for the last 2 weeks and cannot find any resolution.

    I have a dedicated server with a data warehouse company running windows 2003 (standard) using an external IP X.Y.Z.145 subnet 255.255.255.248

    I have a pool of sequential other 5 ip's (same subnet) at same X.Y.Z.146 to 150

    On that server, I have a virtual PC running windows XP professional, configured to use the server's hardware network card (NOT using NAT, NOT using LOOPBACK, NOT using local) - with IP X.Y.Z.146 and same subnet and DNS as the parent server.

    almost everything works well, but here's the point:

    SOME ip's are just not reachable from the virtual child, ALTHOUGH they are reachable from the parent server (anti-virus/firewall/etc... are all turned off on both parent server and virtual child).

    for example,

    www.yahoo.com is reachable in both parent and child.

    www.google.com is reachable with all different ip's on the parent,

    BUT only a small subset of those IP's are reachable on the virtual child.

    there are many other sites which are not reachable as well.

    btw- i tried switching and changing the parent's and child's ip numbers, and got the same effect, REGARDLESS of the ip used.

    I REALLY don't understand what can be the problem... is that a bug? am I missing something?

    PLEASSSSEEEE please save our souls!

    thank you in advance,

    mike

  • manveer -

    It sounds like you are doing the right thing here.  I am not sure why this is not working.

    Casper -

    There should be an option to use the physical network card in your host computer.

    stsf_mike -

    Have you checked to see if the data warehousing company is doing any MAC address filtering / checking?  This may cause the problem you are seeing.

  • Dear Ben, I will check it with them,

    yet tell me,

    if there WAS some MAC filtering,

    wouldn't it block ANY external communications to the VPC?

    After all,

    I am able to connect it from a different country (external IP), and browse a lot of internet pages and ping a lot of IP addresses.

    Can the MAC filtering applied only to SOME IP's? (why?)

    Thank you very much!

    I am looking forward for your reply

    Mike

  • i installed ma laptop with dual boot os - windows 7 and redhat 6.

    then i installed virtual box in redhat 6.os instalkled in virtual box

    is also redhat 6 . i cant ping from virtual pc to my pc somebody plz help

      urgent....

      ajayan1688@gmail.com

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