DSM 7.1 Can't set up SMB when Synology NAS is on a different subnet

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DSM 7.1 Can't set up SMB when Synology NAS is on a different subnet

3
1
NAS
DS218+
Operating system
  1. Windows
Mobile operating system
  1. Android
Last edited:
Hello all,

I've tried searching for this particular problem, but haven't come across any threads regarding this issue. If there is already a topic on this being discussed, I apologize in advance!

My issue is with my Windows 11 machine trying to map a shared Synology drive via SMB. It works perfectly fine when the NAS is on the same subnet (192.168.10.0). However, when I set up the NAS to a different subnet (192.168.20.0), and ensure that ACL rules are set to allow communication between the two subnets, SMB fails to work. I've verified via successful pings both to and from the NAS and Windows machine, and all firewall rules have been set up appropriately--all ports are open, including port 445 which is used for SMB, between the Windows machine and the NAS. I can no longer map the network drive via Explorer, and even Synology Assistant can't find the NAS.

I have configured SMB on the NAS to only work with version 2 and 3, since SMB1 is known to have security risks.

Is SMB just not made to work between subnets? What could I be missing in my setup to allow this to work?

Appreciate any help/advice on this topic!
 
Solution
Well, I sorted the problem out. I ensured that the Windows firewall rules were meant specifically for the NAS IP, not just for the subnet, and I ensured that both the SMB port (445) and the ICMP protocols were set to Allow, for both inbound and outbound rules. In addition to that, mapping the drive via IP address, and NOT the server name, ended up with a successful drive mapping.

Thanks all for your valuable input and helpful advice!!
all ports are open, including port 445
Can you verify that the NAS is listening on that port 445 across subnets? Can you telnet to it or use a PS command to connect to it?

Test-NetConnection -ComputerName targetHost -Port portNumber
 
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I am too having this issue. I have definitely isolated it 100% to the Synology Nas, RS822+.

Desktop/Laptop 192.168.10.x/24
Synology/Asustor4 10.0.50.x/24

I have another AsuStor4 on the same subnet which I can access fine, there are 0 firewall rules blocking that traffic since they are in the same zone.
 
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SynologyTest.PNG
WindowsServer.PNG
WindowsServer-2.PNG
Debian.PNG

my connection test succeeds, I am able to use the share via file explorer \\10.0.50.7\iso and pull a 350mb debian iso, anything larger like windows iso 4-5GB just dies.
 
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Last edited:
Do you have:

LARGE_FILE_SUPPORTED TRUE

Set in your SMB configuration?

☕

[Note that there have been quite a few SMB issues with both W10 and W11 for nearly a year now. Worth testing with a different OS if you can, just to narrow things down a little.]
 
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Last edited:
Can you verify that the NAS is listening on that port 445 across subnets? Can you telnet to it or use a PS command to connect to it?

Test-NetConnection -ComputerName targetHost -Port portNumber
Yes indeed I have port 445 open, here is a snapshot of the connection test:

1690645771346.png


Adding the network drive via IP in explorer works just fine, but file transfer seems slow. Was hoping to get SMB working to have a faster way to move larger folders/files. Or am I mistaken about this? I'm under the impression that mapped drives have much better performance.

Also, my in and out rules for Windows looks like this for SMB:
1690645857698.png


Still no luck in getting a connection established when mapping the server.

Funny enough, I've confirmed that my Android phone, which is connected to the 192.168.10.X subnet, works just fine when establishing an SMB connection via Solid Explorer to the Synology server.

I'm pretty sure this is a Windows issue for me.
 
Upvote 0
Yes indeed I have port 445 open, here is a snapshot of the connection test:

View attachment 13264

Adding the network drive via IP in explorer works just fine, but file transfer seems slow. Was hoping to get SMB working to have a faster way to move larger folders/files. Or am I mistaken about this? I'm under the impression that mapped drives have much better performance.

Also, my in and out rules for Windows looks like this for SMB:
View attachment 13265

Still no luck in getting a connection established when mapping the server.

Funny enough, I've confirmed that my Android phone, which is connected to the 192.168.10.X subnet, works just fine when establishing an SMB connection via Solid Explorer to the Synology server.

I'm pretty sure this is a Windows issue for me.
Tried this on my 2022 macbook pro does the same thing connected to the .10 network and just stops copying.
 
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Or am I mistaken about this? I'm under the impression that mapped drives have much better performance.
mapped drive or a manually used UNC (\\ipaddres\path...) work the same. SMB as a protocol is used in both cases and the mapped drive is there to a) help out in terms of usability, b) present a location as a "local" drive (as some apps require it).

I'm pretty sure this is a Windows issue for me.
Well, I would say so as well, considering that another device on the network works fine. Still, saying that more testing would be needed.

Can you spin up an Ubuntu ISO and try and use that OS in the same situation on that same PC? Just to see if the source and destination on a separate OS would behave differently using the same hardware?

my connection test succeeds, I am able to use the share via file explorer \\10.0.50.7\iso and pull a 350mb debian iso, anything larger like windows iso 4-5GB just dies.
Now this is just me spitballing here:

SMB setting on the Syno side?
Any antivirus on either end?
Considering that Asustor works, guessing the drives, network, etc is not the issue. One more thing, have you tried maybe copying using a 3rd party software? Total Commander or something similar? What happens when you try and copy that data over a different protocol, like FTP?
 
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mapped drive or a manually used UNC (\\ipaddres\path...) work the same. SMB as a protocol is used in both cases and the mapped drive is there to a) help out in terms of usability, b) present a location as a "local" drive (as some apps require it).


Well, I would say so as well, considering that another device on the network works fine. Still, saying that more testing would be needed.

Can you spin up an Ubuntu ISO and try and use that OS in the same situation on that same PC? Just to see if the source and destination on a separate OS would behave differently using the same hardware?


Now this is just me spitballing here:

SMB setting on the Syno side?
Any antivirus on either end?
Considering that Asustor works, guessing the drives, network, etc is not the issue. One more thing, have you tried maybe copying using a 3rd party software? Total Commander or something similar? What happens when you try and copy that data over a different protocol, like FTP?
I'll give 3rd party software a try. I will also try my macbook from another VLAN connected to the synology 1gb lan port. The 10.0.50.x nic is one of those Synology 10GB adapters (with the cache drives) and for whatever reason might be an issue.
 
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cross subnets seems to be the issue here FYI....which my first guess would be firewall....but 1) they are in the same lan zone...2) asustor works....3) im able to map the drive and navigate the share and copy smaller debian iso's. if firewall was blocking the connection I shouldn't be able to even get to see or map the share
 
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The 10.0.50.x nic is one of those Synology 10GB adapters (with the cache drives) and for whatever reason might be an issue.
Official PCI expansion card you mean?

if firewall was blocking the connection I shouldn't be able to even get to see or map the share
Correct. Testing with another device like you mentioned a Macbook might be a good test as well to see if this is indeed a Syno issue or Windows one.
 
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Official PCI expansion card you mean?


Correct. Testing with another device like you mentioned a Macbook might be a good test as well to see if this is indeed a Syno issue or Windows one.
yeah it is a Synology E10M20-T1, i have already tried the macbook cross subnet to the 10gb adapter and it does the same thing just dies.

What i will try now is cross subnet with the mac & desktop but to the built in 1GB adapter.
 
Upvote 0
Well, I sorted the problem out. I ensured that the Windows firewall rules were meant specifically for the NAS IP, not just for the subnet, and I ensured that both the SMB port (445) and the ICMP protocols were set to Allow, for both inbound and outbound rules. In addition to that, mapping the drive via IP address, and NOT the server name, ended up with a successful drive mapping.

Thanks all for your valuable input and helpful advice!!
 
Upvote 0
Solution

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