Big Sur and SMB Issues

I am having the same issue. Connecting to a remote server via SMB over a VPN. We get disconnected from the server (But not the VPN). When transferring files or opening files after about 5-8 minutes of using the server we get disconnected from the server itself. I can see this in real-time because I have a Terminal window pinging the IP of the server and I can see when it gets disconnected. I found this article which did seem to help. https://support.apple.com/en-us/HT208209. However, after a day of working very well, the problem persists.

I have 2 brand new iMac Pro's we literally purchased this year that are both experiencing the same exact issue. This is ironic because only the iMac Pro's are the only machines having the issue. We have Mac Mini M1's and Mac Pro Towers that work perfectly fine.

Considering we live in a mostly remote society today to earn a living it's critical we have a stable Server connection. Since most business servers are typically windows based SMB is crucial.

Please help Apple.

Same issue here over SonicWall Site to Site VPN to Windows 2016 server. Only with m1 silicon macs. With Intel it is okay.

https://discussions.apple.com/thread/252710313

IpSec Client IPsecuritas and SSL VPN Client mobile connect are okay with m1 silicon macs.

I am having the same issue and it's annoying. I had a backup of a NAS device to a TB3 connected 8TB hard drive while online taking a final for a college class. There was an SMB error, and it kicked me off my wifi. So much for my final.

I am seeing reports since Sept of this same issue on the internet. When will Apple get this fixed?

I had uninstalled our VPN before posting, and it's a little better, but the problem is not resolved

I also use Box, Norton LifeLock (no VPN) and iCloud, so not sure if they are interfering with networking

I have the same problem. Any upload of a file to the smb server causes havoc with the network connection and I end up having to reboot. I am using Cisco Any Connect VPN. When I am at work not using the VPN things seem to work ok. It is only at home with the VPN that it happens for me.

That's interesting. I have no VPN installed, so I only access the NAS when not using VPN. I can download files > 200GB, but trying to upload something as small as 5MB to the NAS messes up all networking. I have to reboot to reset networking to even use Chrome. Not like I have old hardware either, I'm using a 16" 2019 Macbook Pro with an i9 and 16GB RAM.

Just to chime in, I am having this same issue on a new M1 MacBookPro, macOS 11.2.3 (20D91) through our VPN via Cisco AnyConnect 4.9.02028 (which as someone mentioned earlier is the latest our central IT group is providing). I will have to go in to campus to see if it occurs without the VPN in the mix.

I have this problem also (try to copy a file to Windows PC from 2017 Mac on Big Sur). This occurs on my home network with a "standard" ASUS home router / wireless access device. Try to copy file (SMB) to PC, process hangs, MacBook disconnected from network, reboot of Mac required. Strikes me as a Big Sur issue.

Same problem here on a new Silicon MBA2020 with 11.3 on it.

SMB over a Site to site VPN Connection breaks or can't connected.

Usercredentials are wrong, no access to any directories

Sometimes I can see in the Finder that the connect was login with the AppleId from this account.

Here is something wrong.

We're seeing a similar issue with our network. We've got several different SMB servers, including an older Isilon, Windows server, and Liiix-based NASs. If you're on our local network, all will mount just fine. HOWEVER, if you're on the VPN (Palo Alto GlobalProtect), you can't mount from the Isilon. Fails at the auth.

We've looked hard at the firewall logs, but there's nothing apparent. It's really odd that only that one type of SMB mount fails, and only over the VPN. It is SMB v1, but if that were the issue, then it wouldn't mount locally either.

May 17, 2021

OMG! This thread is the closest I've seen to a Mac-SMB problem I've had in various forms for years. I've torn my hair out and cursed Apple countless times for pathetic SMB service and no official tutorials that I've seen on how to deal with its implementation of Samba and the innumerable tweaks it has introduced.

The latest version: M1 MacBookAir 2020, Macos 11.2.3. SMB served up from Synology 716+ (latest DSM [6.2..?].). No VPN here. First problem: transfers pathetically slow, though slightly better after implementing a couple of the common "how-tos" posted around (e.g. no signing, vfs:fruit on the server, ...) - it's like an old 56k modem. Biggest problem: with files from the server open, suddenly the machine seems to lose track of them, tell me it doesn't know where they are, that I don't have permissions for them, and I'll need to duplicate the local files and resave back to the server. This is no way for a megabillion dollar computer company to provide network capabilities. My old OS/2 box did better. My OpenSuse computer is flawless and greased lightning connecting to the Synology.

Might there be some problem introduced by the new file structure Apple has created?? Automounts appear to work fine once the maps are changed for the new mount point (/System/Volumes/Data/...). But they seem to be less than robust.

Sorry for the rant... first chance I've had to let off steam. In short, SMB is *very* frustrating on Mac, even M1.

May 25, 2021

Having posted this particular rant, I see it as only fair to report back on some success. In an effort to find some remedy to the slow, unstable SMB on my M1 Macbook Air, I had followed the extensive testing by one user (rolande.wordpress.com) to modify a number of TCP system settings via sysctl. In particular, for High Sierra and Mojave, the suggestion was to use the following values (NB: these seemed *not* to help, perhaps make things worse):

net.inet.tcp.mssdflt=1448

net.inet.tcp.blackhole=2

net.inet.tcp.slowstart_flightsize=60

net.inet.tcp.sendspace=3125000

net.inet.tcp.recvspace=3125000

net.inet.tcp.win_scale_factor=6

net.inet.tcp.autorcvbufmax=3125000

net.inet.tcp.autosndbufmax=3125000

By chance I neglected to run the script setting these values shortly after my original posting, leaving the default values set. Since then, my SMB connections have been very stable with tolerable speed. It is slower than my OpenSuSE machine, but it is not disruptive.

What *did* make a difference, with the Synology, at least, was the server and client settings suggested at this article (https://tinyurl.com/2rwh257h) at tech.setepontos.com, especially the vfs:fruit module on the server.

Similar issue here over Cisco AnyConnect VPN. Just upgraded to version 4.10.01075 and the problem persists. Connecting SMB to two IP addresses at work, a Windows server and my iMac in the office, produces difference results. The Windows server connection drops after 3-5 minutes whether there's activity (copying files, etc.) or not. However, the iMac connection stays connected just fine. The VPN connection stays stable through it all.

Thoughts? Does this behavior – Windows server connection drops while iMac connection doesn't – give anybody any ideas? I'm stumped.