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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 to 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?

Category: Entry Level Firewalls

Best Answer

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    frodooftheshirefrodooftheshire Newbie ✭
    Answer ✓

    Turns out it was an issue with the customer's Comcast equipment. Replacing it resolved the issue.


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    MitatOngeMitatOnge All-Knowing Sage ✭✭✭✭

    are you using "TCP STREAM SCANING via GAV" or CATP with DPI-SSL

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    MitatOngeMitatOnge All-Knowing Sage ✭✭✭✭

    could you close this topic as RESOLVED please?

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