First off let me say I know this has been a frequent question posted here regarding slow upload speeds on the UTM. I have been a UTM user for well over a decade probably closer to 15 years. I may not be a Bob expert but I know my way around the software.
I recently got an ATT symmetric 1GB fiber line and plugged it up to my UTM VM. At first, performance was normal and expected. I was getting close enough to max throughput with the understanding that I would be getting less because it was running in a VM on older hardware. All fine. Then one day, and I honestly don't know when, upload performance just took a nose dive. I would get 3-5Mbps on uploads. Sometimes spiking to 7%.
I did all the normal things, turned off IDS, turned off web filtering, confirmed 1500 MTU on all NICs, you name it. I have a small Ubiquiti FW as a backup and it was able to get full 1Gb from all my VM's and my physical boxes, so I know my internal network is fine and can handle it. I even built not 1 but 2 brand new UTMs. One I did a restore of a config and another I did unconfigured, no settings. The performance of all these UTMs is the same 5Mbps upload. Download speeds are fine and close to theoretical maximums. I am at a complete loss. I do NOT want to migrate my services to Ubiquiti. I want to keep using the UTM. What else can I do? there are no IDS or filtering logs to check since all of that is disabled. Is this an ATT thing? Is there some special setting I need to make on the ATT FW or UTM interface setting I need to make to get this to work? It doesn't have to be perfect, but symmetrical upload is all I want.
I've never heard upload speeds being an issue with UTM, just the downloading from the poor implementation of single thread snort use which no one seems to want to upgrade to multi threading. :/
Anyways, the only thing I've heard about upload issues with ATT Fiber (which is almost in my area, so I can't wait) is a setting on NICs that are enabled - Large Offload IPv4 (v2). Disabling that apparently fixed upload speeds. Not sure if UTM supports that feature or not, but your VM might?
Worth a try to find and disable that.
UTM - 9.713-19 64-bit | Intel Xeon 4-core v3 1225 3.20Ghz 16GB Memory | 500GB SATA HDD | GB Ethernet x5
Good thinking. Went looking but there is not a place to configure that at least not in the VM. I do have some 1GB links in a VSS on my ESXi host that I can host at least for the Internal network. I moved the NIC over there and there was no difference.