virtualbox.org

I've checked the topics back to the 10th for something similar and have not seen a report for this.

First the nitty gritty details of the installation:
I installed 3.0.2 over a 2.2.4 installation. Host is XPSP3, Guest is XUbuntu 9.04. VT-x/AMD-v is turned on. First thing I did was install the new guest additions and reboot. PC-NET III adapter w/NAT. In the guest I am using OpenVPN to tunnel to a real Debian box and then out from there.

Under 2.2.4 I had no problems with the network speed. Everything was snappy and responsive.

Under 3.0.2 it seems like every other network connection would fail to work. TBird would fail one check (IMAP folders) but the next operation would work. In Firefox it was almost like clockwork. Enter a URL and it would just sit there spinning its working icon. Stop and reload, it instantly goes through. Click on a link, sit and spin. Stop, click on the link again, it would instantly go through. I tried it both with 2 CPUs (real machine has 2 cores) as well as stepping back to 1 CPU and IO-APIC turned off (similar to 2.2.4's settings). Same issue both ways.

I reinstalled 2.2.4 but am still running the 3.0.2 guest additions. Networking is perfectly fine again. Every TBird check goes through. Every URL click in Firefox works.

Quick update. I did see mention that trying the Intel virtual adapter might work better. Reinstalled 3.0.2 and switched the adapter over, still having the same intermitent issue in Firefox. ~50% of the links clicked just sit and spin. Stopping and clicking again will get it to go through instantly.

Also, the above behavior is not reflected in pings. I run an MTR to a machine a good 12 or so hops out on the net and get all the pings back without any major hiccups.

Hmm. Mine guest network also changed practically unusable after I installed 3.0.2 over 3.0.0. Host is Windows Vista x64 and guests are Arch Linux & WinXP SP3. I pinged from guest OS couple servers and got 10 - 50% packet loss every time. Pinging from host to same severs seems to be working fine. Changing network adapter or connection type didn't have any effect.

I experience pretty much the same kind of behavior: Host is XP Pro, Guests vary between XP Pro, Windows 7, Ubuntu and other Linux distributions, VirtualBox version 3.0.2:
Any attempt to use a web browser is annoying at best, with many timeouts or if successful, VERY sluggish behavior...
Bittorrent clients demonstrate weird behavior too, as LAN connections seem to work ok but connections to the internet peak out at about 1/4 of max speed with falling down to 0 kb/s in regular intervals like a sinus wave...
...strangely enough downloads like the occasional auto-updates of Linux seem to use full bandwidth, though not without hiccups or even timeouts when starting the transfers or updating the repository lists...

As far as I could see it didn't matter what type of adapter I choose nor if NAT or Bridged Adapter was selected...

As I never had such problems with pre 3.x versions of VirtualBox but rather flawless network performance, I expect these to be early problems of a new release that hopefully will be taken care of soon - my hope is that the developers are aware of these kinds of problems...

Most network problems are in fact traced back to the virtual network adapter, especially in 3.0.x and up.
A great amount of people have corrected this by selecting the IntelPro/1000 T server adapter in the guest settings.
If trying this does not help you should search bugtracker for an open ticket and add yourself to it.
Link to bugtracker is at the bottom of my post. You will need to setup an account there though as it is on a different system.

Thanks for the quick reply - some testing for the last few hours didn't turn up any big difference between PCnet-FAST III and IntelPro/1000 T server where it comes to performance - subjectively it seems slightly better and more responsive but even if it is rather more than a subjective observation phenomenon it's nowhere near the performance and responsiveness it used to be with version 2.x or the host OS - bugtracker didn't turn up anything that fits exactly my observation, but I didn't have time to check all possibly related recent tickets yet...

If changing to the Intel adapter has fixed the problem of it slowing down and having a lot of collisions, and latency then the next set is to tune the client adapter for the best performance.
Windows machines are tuned to be slower than they should be to ensure accuracy but really pull down the speed by doing this. Changing the MTU and the RWIN
http://www.dslreports.com/faq/6266 will help. As well as you need to check the MTU on a Linux client. It may not be set to the best setting. (Auto usually means less) Start with 1500 for the MTU and then drop it (4) each time until you find the sweet spot.

The NAT networking problem in Vbox 3+ has been discussed

http://forums.virtualbox.org/viewtopic.php?f=20&t=19436

and reported as a bug:

http://www.virtualbox.org/ticket/4343

It has been reported that an early version of 3.0.3 still has the problem.

However, a new bug should probably be opened for your specific host/guest configuration.

I switched to Intel PRO/1000 T server and Bridged Adapter (eth0) and it made a world of difference.

Previously a simple would timeout on the first attempt and then work and fast the next. It was not a DNS server problem though because all other (real) machines on the same network had no problems with DNS.

HTH
Dany