Windows
Slow internet only while connected to VPN
Internet speed slowed down at home only when connected to VPN, and returned to normal when VPN was disconnected. The technician disabled Receive Side Coalescing (RSC) on the Ethernet adapter, which resolved the issue.
Killed once by someone from XL.net, on 2026-01-12.
Affects
Apps
- SonicWall Global VPN Client
Hardware
- Ethernet adapter
What you see
- Internet speed is very slow only while connected to VPN.
- Disconnecting from VPN restores normal internet speed.
Why it happens
Likely Windows network adapter RSC settings were not working well with the VPN client, causing the slowdown.
When it shows up
A Windows computer has slow internet only while connected to SonicWall Global VPN Client VPN sessions.
You are in this case if:
- Ethernet adapter has Receive Side Coalescing (RSC) enabled.
- Slowdown stops when VPN is disconnected.
1 fix below
The steps that killed it
The steps are behind a quick check
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Keeping it away
- If the slowdown returns, reboot after the RSC change and retest VPN connectivity.
Someone from XL.net killed this on a Windows computer on 2026-01-12. It is written up from that one repair, so it cites no outside page.