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10.7: A possible workaround for VNC issues System 10.7
Here's a workaround for some VNC issues that may appear with Lion.

A quick search will show a growing list of users having issues with VNC in Lion. See, for example, this Apple Discussion thread.

These same issues do not exist with Leopard or Snow Leopard. In testing to make sure our network wasn't part of the problem, we tried to VNC to a system over our VPN from outside our office. Lo and behold, it worked. The same laptop on the local network would get absolutely unworkable performance on the local wired or wireless network, but would work just fine over our Cisco VPN (but using the builtin VPN options for the Mac, not the Cisco VPN client) from outside our campus. That caused us to try having the system connect to our VPN while on the local campus and sure enough it worked as well. There appears to be something about the virtual interface that's created that works whereas using the default en0 (wired) or en1 (wireless) interfaces are problematic.

We haven't deduced the actual problem just yet, but we think we're onto something related to either the virtual interface and/or the statefulness of the VPN connection.

In any case, if you're having performance problems using VNC to access another system (Mac, PC, or Linux) from a system running 10.7 and you have a VPN, try connecting to it and see if it resolves your issues.

[crarko adds: I use Apple Remote Desktop and have not observed this. Judging from the results of the search above, it does seem to be a widespread issue for VNC clients. It looks like there was a bug report files with Apple on it, but it's not clear if the issue is still present in 10.7.2. Give it a try and let us know in the comments. Also, give the proposed workaround a try if you can and see if that helps. There's an awful lot of new networking code in Lion and it's become clear that it will take some wringing out in the field before it's all working as intended.]
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10.7: A possible workaround for VNC issues | 9 comments | Create New Account
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Bug inApple Screen sharing
Authored by: SOX on Oct 19, '11 07:42:59AM

If you use apple screen sharing and the remote machine has two different sized monitors set to mirror, it won't work.

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Bug inApple Screen sharing
Authored by: mjperson on Oct 19, '11 07:49:06AM

In my case, it works, but all of the mouse clicks land hundreds of pixels off when the second monitor is connected. Dropping the machine back to one monitor before connections fixes everything, and I've heard putting the native monitor on the left also fixes things, but that's not feasible for my setup.

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10.7: A possible workaround for VNC issues
Authored by: SteveDemy on Oct 19, '11 08:04:24AM

I had inconsistent VNC performance connecting from Lion Screen Sharing clients to Lion servers after upgrading. Failures to connect, slowdowns, hangs. Connecting from the same Lion clients to 10.6.8 servers worked perfectly. The solution, in my case was to clean up the keychains in each of the Lion macs, ensuring that only keychain entries created in Lion remained - nothing pre-migration. That completely solved the VNC problem and similar inconstancies I was having connecting to VPNs. I'm not sure which keychain entries were the culprits, but those associated with the wireless network interfaces are most suspected. Perhaps Apple's change from "Airport" to "Wi-Fi" is the underlying cause?

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10.7: A possible workaround for VNC issues
Authored by: kiltbear on Oct 19, '11 09:34:24AM

Is this running a 3rd party VNC, like Chicken of the VNC?

Have you tried it with the internal VNC client "Screen" buried in /System/Lbrary/CoreServices?

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10.7: A possible workaround for VNC issues
Authored by: spinkb on Oct 19, '11 10:13:12AM

Starting with 10.7.2, if I try and connect to my main iMac using screen sharing, it just sits there trying to response. About 30 seconds later, the machine kernel panics and reboots. I sat here with my laptop next to me and tried it, then for 30 seconds browsed the web, pinged machines, etc...machine seemed OK, then the kernel panic and reboot.

10.7 had issues where the "vnc://" in the Finder didn't always work too...completely different machine I had those issues on.

So, screen sharing and VNC with it in 10.7 are quite unpredictable, unreliable...and now downright dangerous. Who would expect a kernel panic for doing VNC? The kernel panic is new as of 10.7.1 or 10.7.2...not sure which.



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10.7: A possible workaround for VNC issues
Authored by: Supp0rtLinux on Oct 19, '11 02:24:08PM

I'm the submitter of the hint...

Our scenario is any Mac trying to VNC to a Linux system here on campus. The remote Linux system (CentOS)has only one monitor. We're using the built-in Screen Sharing app (Finder, Apple + K, vnc://hostname). Leopard and Snow Leopard can connect to the Linux host just fine. A Windows PC with TightVNC or RealVNC can hit the Linux PC w/o issue. Built another Linux system for testing and had the same results. 10.7.2 doesn't resolve the problem. The problem is specifically with Lion systems trying to VNC to a remote system. Google searches verify this. Ironically, my 10.7.2 Mac has piss poor performance trying to VNC to this Linux system, but I can VNC from my Mac to my Mac Mini at home on my home network w/o issue. The VPN solution is the only thing that's worked on our local campus and we just stumbled upon it. We're using Wireshark and Cisco NAM to try and isolate things further... perhaps the virtual interface of the VPN or the statefulness of the VPN connection are factors. Also, we're using the built-in VPN connection with the Cisco settings, not the Cisco thick client nor the AnyConnect client.

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10.7: A possible workaround for VNC issues
Authored by: meikokun on Oct 19, '11 02:43:29PM

whilst Im able to access a lion machine from my SL laptop, and from that Lion machine, Im able to access a tiger system, for some reason, in their restful state the tiger machine is sending zero data, but the lion machine is pumping it out at a meg a second. This is on our n-network.

ok, a bit more testing, and it seems that on closing the tiger vnc connection, the data output from the lion box dropped to 10k/sec. it seems that the clock running on the tiger computer was causing lion to refresh that entire desktop, and then pump out that image over vnc constantly.

by turning off anything at all updating on the lion system (seconds on the time, istat menus refreshing) data has now trailed off to zero whilst resting.

moving windows around like crazy otherwise not a problem, responsiveness perfect. Could it be lion is just incredibly inefficient at screen redraws for vnc?

maybe someone can install a different vnc server and see if that works better. if no one else does before the weekend, Ill have a go myself.

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10.7: A possible workaround for VNC issues
Authored by: joekewe on Oct 20, '11 09:09:03AM

Initiating a VNC connection from my iPad to a 10.7.2 desktop over a local network slowly shows the initial grey linen screen with user badges. Clicking on my user brings the password oval. I can either type a couple of characters or just watch the cursor blink a few times before the connection stops dead.

Screen Sharing app from a 10.7.2 machine to a remote 10.7.2 MBP with second, different-sized monitor works. So does a remote connection to a 10.6.8 machine. I'll try cleaning keychain entries as someone else suggested, but that won't help the iPad.

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10.7: A possible workaround for VNC issues
Authored by: joekewe on Oct 20, '11 09:24:19AM
Restarting the screen sharing / ARD services per just worked for me.

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