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<p class="MsoNormal"><span style="color:#1F497D">Hi Maxime,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks a lot for the response.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">This is quite an old software which has been using this series of IP address (like 127.2.x.x and 127.3.x.x) for VM to VM communication.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Unfortunately the software has a lot of dependency on this and same software code is shared between many products.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">So it looks tough to redesign this part.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">We were running this successfully on VirtualBox 3.0.14 and VirtualBox 3.1.8 without any issues.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Recently the linux kernel in guest VM was upgraded from 3.0.14 to 3.14.75.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">After this we started seeing strange disk corruption issues on VirtualBox 3.1.8<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">i.e we do parallel copy of large files (around 2GB) to 5 VMs in parallel and in one of the VMs (randomly) we see that the md5sum is different for the transferred file.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The file size is shown correctly after the copy.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The strange part is that on each subsequent ‘md5sum’ of the same file (without again copying) yields different results.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The disk for each VM is stored as separate vdi files on the host disk.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">We use SATA controller configuration on the VM for disk access.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">This issue is not seen on VirtualBox 5.0.10.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">But then we have the issue that VM to VM communication is failing since 127.x.x.x is getting blocked on VirtualBox 5.0.10.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Best Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">George<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="color:windowtext;mso-fareast-language:EN-IN">From:</span></b><span lang="EN-US" style="color:windowtext;mso-fareast-language:EN-IN"> Maxime Dor [mailto:max@kamax.io]
<br>
<b>Sent:</b> 01 December 2015 18:30<br>
<b>To:</b> vbox-dev@virtualbox.org<br>
<b>Subject:</b> Re: [vbox-dev] VirtualBox blocks 127/8 (loopback) subnets for intnet<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi George,<br>
<br>
If you mean IPs like 127.x.x.x, they are dedicated to localhost communications by the TCP/IP standard and described as such in
<a href="https://tools.ietf.org/html/rfc990">RFC 990</a>:<span style="font-size:12.0pt;mso-fareast-language:EN-IN"><o:p></o:p></span></p>
<pre>The class A network number 127 is assigned the "loopback"<o:p></o:p></pre>
<pre> function, that is, a datagram sent by a higher level protocol<o:p></o:p></pre>
<pre> to a network 127 address should loop back inside the host. No<o:p></o:p></pre>
<pre> datagram "sent" to a network 127 address should ever appear on<o:p></o:p></pre>
<pre> any network anywhere.<o:p></o:p></pre>
<p class="MsoNormal" style="margin-bottom:12.0pt"> <br>
You are lucky it ever worked in the first place, most likely because of poor software implementation.<br>
I'm not aware of any way to make it work again and you should definitly NOT try to make it work again.<br>
Use 10.0.0.0/8 if you need such a big subnet, else go with 172.16.0.0/12 or 192.168.0.0/16<br>
<br>
Max<o:p></o:p></p>
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<p class="MsoNormal">On 01/12/15 13:43, <a href="mailto:george.vargh@wipro.com">george.vargh@wipro.com</a> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">We are having our test topology running multiple VMs on a server.<o:p></o:p></p>
<p class="MsoNormal">The guest VMs are linux based and the host is based on RHEL 6.4.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">The eth interface of VMs are interconnected via ‘intnet’ NIC settings.<o:p></o:p></p>
<p class="MsoNormal">The VMs are using 127/8 IP addresses to communicate with each other.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">We are currently using VirtualBoX 3.1.8 and everything works fine.<o:p></o:p></p>
<p class="MsoNormal">But when we upgrade to latest VirtualBoX 5.0.10, we observe that the 127/8 IP addresses are being blocked and it does not reach the VM interfaces.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Based on our testing, it looks like this behaviour is seen from VirtualBox 3.2.0 onwards.<o:p></o:p></p>
<p class="MsoNormal">Can you please suggest if there is a way to get these IP address to be allowed?<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Best Regards<o:p></o:p></p>
<p class="MsoNormal">George<o:p></o:p></p>
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