I have an ubuntu 9.10 machine running as a virtualization host. I am having problems when network clients download from the guest. This only happens when the VMs use bridged mode networking. If I use NAT, then the speeds are fine.

Note that its only network clients downloading from the guest that is slow. Everything else has expected speeds. Speeds are:

host <- guest: 66 MB/s
guest <- host: 36 MB/s
host <- net: 63.4 MB/s
net <- host: 50 MB/s
guest <- net: 25 MB/s
net <- guest: 1 MB/s

This problem occurs with vmware guests and virtualbox guests, which makes me think this is some kind of problem with my networking setup/hardware than a problem with my VMs.

I have tried the following, all without any change in the problem:

* multiple network clients
* added a different gigabit NIC to the host and bound vm bridged network to that interface
* tried doing the transfer on port 8080 instead
* tried briding the VM nic to a different NIC than what the host is using for most communications (i.e. I had two network cables plugged in)

Just tried a linux guest and didn't have any download problems.

Then maybe list HW specs and configuration details for both the virtualization host and a generic guest setup?


This means your other guests aren't GNU/Linux?

1 members found this post helpful.

unSpawn, thanks for taking a stab at this. After installing multiple flavors of ubuntu as well as slackware on three different machines and seeing the same problem occur each time, I finally hit on something. The problem was only apparent when it is a Windows 7 guest and a windows network client. If either the guest or network client is linux, then I don't have the problem.

Not sure what else to do, so I filed a bug with virtualbox:

http://www.virtualbox.org/ticket/5812

Although I think it quite odd that vmware has the same problem. Throughput between native windows clients on my network is not that slow.

Update: I did some testing with the network connection settings on my vista network client. It had an entry for "Deterministic Network Enhancer" (DNE). When I unchecked that item, download speeds from the windows guest came in at 16-20 MB/s. FYI, the DNE is part of VPN clients including Cisco's client.

My windows 2003 box does not have that entry and the downloads are still in the 1-3 MB/s range.

DNE apparently is some type of firewall-like SW from Citrix (http://www.citrix.com/lang/English/lp/lp_1680845.asp). W2K3 might have some QoS or other bandwidth-managing driver loaded but there's no details posted (besides if it is about mcrsft it might not appropriate for the Linux Networking forum).