Upload bandwidth drops after 18-20 mins
Good morning. Last week I discovered a strange occurrence with one of my client's networks. I apologize for the long explanation.
Setup is Comcast Gateway -> SonicWall TZ350 - Unifi USW-48-POE switch. I had just setup a new Veeam backup solution onsite that was uploading files to my VCC partner, and I heard their remote users connecting over SSL VPN were experiencing slow RDP sessions/disconnects.
Customer has 25 Mbps of upload bandwidth and I have traffic rules setup in Veeam B & R to limit upload bandwidth to 15 Mbps.
Anyways, after much troubleshooting here's what I discovered: Running a speed test (without backup running) was showing only 6-10 Mbps of upload bandwidth.
If I restart the SonicWall it goes back to 23-25 Mbps (full upload bandwidth). Then after about 20 minutes the upload bandwidth goes back to 8-10 Mbps.
Bandwidth management on WAN interface is disabled. During the initial 15-20 minutes where upload bandwidth is full speed, I can run the Veeam backup at full throttle (no traffic rules) and still easily connect via SSL VPN and access a computer over RDP with zero lag/dropouts. It's like the upload isn't even occurring.
Again, I can even watch in task manager on the backup box that ethernet is using all 25 MBps of upload, and then after about 18-20 minutes I'll watch the bandwidth in task manager go back to 8-10 Mbps and then my RDP session to the other box becomes garbage - the screen refreshes become nonexistent, and then I start to get dropouts. I probably did 5 different restarts and each time it was the same - so it wasn't a onetime occurrence.
Troubleshooting wise I updated the SonicWall from from 220.127.116.11-83n to 18.104.22.168-93n and even loaded a past configuration to see if there was something wrong with the current config. None of this made a difference.
I've never seen anything like this. Any idea what might cause this?