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Linux - Virtualization and Cloud This forum is for the discussion of all topics relating to Linux Virtualization and Linux Cloud platforms. Xen, KVM, OpenVZ, VirtualBox, VMware, Linux-VServer and all other Linux Virtualization platforms are welcome. OpenStack, CloudStack, ownCloud, Cloud Foundry, Eucalyptus, Nimbus, OpenNebula and all other Linux Cloud platforms are welcome. Note that questions relating solely to non-Linux OS's should be asked in the General forum.

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Old 08-26-2013, 04:39 PM   #1
themrrobert
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Unhappy Strange Issue: Internet only half-works on virtual machine. Web browsing, no download


Here is the situation:

I have a hypervisor running fedora 18 (el6) with virt-manager.

I actually have 2 of these hypervisors, one is a dell 2950 (svr A), the other is a super insanely beefy R810 (svr B) or similar.

The dell 2950 works great, perfect, but on the 'better' machine, this is the story:

1) i tried copying the image of an existing windows VM from server A to B, and noticed that i couldn't download anything.

I was able to get to webpages, but when a download started, it might get the first return packet, so it thinks its going like 57 byes per sec, but it won't get anything else.

Then, trying to access our NAS (via smb) it will show files, but i can't copy them over. Only tried to copy 2MB of data, and i only got the first few kb, then it just waits indefinitely.

I installed a completely fresh VM, from the iso image, and it has the exact same problem.

I checked, i'm using the same nic settings on both:
"Host device em2 macvtap"
"Bridge"
"Hypervisor default"

I also tried each of the alternative device types but nothing works.

I tried sniffing the traffic with wireshark, and i can see some retransmissions, but i wasn't able to figure out the cause.

Any ideas? I am about to deploy an asterisk VM from the same Hypervisor B, and this network not working on a windows 7 VM is a hugely scary issue, especially considering i already spent several hours configuring the new server.
 
Old 08-26-2013, 08:52 PM   #2
PTrenholme
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Location: Olympia, WA, USA
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I've noticed that a software update to any VM under the virt-manager seems to "choke" after about 20 seconds (about 120Mbits on my connection), and halt for 60-120 seconds before running another 20 seconds. This makes the updates quite tedious, so I just let them run while I do other things.

It's might be a "bug" introduced in an attempt to prevent resource hogging by the VM, but what I haven't been bothered enough by the problem to look at the code or investigate any further.
 
Old 10-10-2013, 04:47 AM   #3
whytigr
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have you tried setting iptables -A FORWARD -m physdev --physdev-is-bridged -j ACCEPT

or setting rp_filter to 2 in /proc/sys/net/ipv4/conf/vnetNN?

I've seen this issue in Centos 6x and I maybe FC-18 as well. newer libvirt/kvm/kernels don't have the issue so it's been a while.

check for mac address 01:80:* in wireshark/tcpdump/ngrep etc as this is indicator of misconfig and/or too much traffic through the router. turn on STP and/or tweak /proc/sys/net/ipv4/conf settings or better yet upgrade to FC19+

~~Tigr~
 
Old 10-11-2013, 11:55 PM   #4
PTrenholme
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Quote:
Originally Posted by whytigr View Post
[...]
I've seen this issue in Centos 6x and I maybe FC-18 as well. newer libvirt/kvm/kernels don't have the issue so it's been a while.
[...]
Thanks for the suggestions: I haven't noticed it on F-19, F-20 or F-21, and, as I said, it didn't much bother me.
 
Old 10-24-2013, 05:57 PM   #5
ericson007
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Whytgr beat me to it. I solved a similar isue by enabling stp on the bridge. You can use brctrl or edit the bridge config directy.

You can check current status of stp with

Code:
brctl show
 
  


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