Help wanted - Connection limit with Filezilla server 1.7.2

[kc730]

I've recently upgraded/rebuilt my server from VMWare (Windows 2016 VM with Filezilla server 0.96) to Hyper-V (Windows Server 2022 with Filezilla server 1.7.2). I'm now experiencing an issue where Filezilla server only seems to handle up to 10-12 concurrent connections, when previous I could handle a lot more.

I've updated Windows firewall to allow Filezilla Server to run, as well as also tried disabling Windows firewall but the issue persists. I can't for the life of me figure out why and how to increase the connection limit. Can anyone point me in the right direction?

[botg]

How many CPU cores have you assigned to the virtual machine?

[kc730]

How many CPU cores have you assigned to the virtual machine?

I've assigned 8 cores the same as it was when I had Fillezilla server 0.96 running on VMWare. I then upped it to 24 cores to see if that changes anything, and still only seeing Filezilla server allowing 10-12 connections at most.

[oibaf]

When you say "allowing", what do you actually experience? Are the excess connections refused? Are they in a sort of waiting state and then they time out? Do these connections show up in the log files?

[kc730]

When you say "allowing", what do you actually experience? Are the excess connections refused? Are they in a sort of waiting state and then they time out? Do these connections show up in the log files?

What I see is connection accepted/transferring files, and once I see/count about 12 active connections I start noticing at least 2 of those active connections turn into "idle" and disappearing of the list and replaced with a new connection. Upon logging onto the source location to check the transfer there, its changed to Failed connection which required me to manually restart.

However, upon attempting to restart that connection, I see 1 of the 12 active connections to change to idle, disappear and then replaced with the transfer job I just restarted. I'm certain its not timeouts, as I've tried setting those to 60 minutes.

Essentially I'm using Filezilla to replicate backup images from around 20 or so different sites concurrently to our FTP server. But with the new upgrade, only 10 active connections can be made at a time.

[oibaf]

When you see a connection in "idle" state it's because it is not transferring anything. If it then disappears, it's either because the (in)activity timeout kicks in, or because the client decides that it's time to go.

What do the server's log say about these connections? Set the log level to "5 - Debug", then take notice of the session id of one of these idling sessions and look for the same session id in the server's logs. Isolate that specific session and paste the whole sequence here in the forum. Feel free to redact the IP address or other data you might think it's sensitive, but do not alter the log file in any other way.

[kc730]

I believe I've identified my issue and resolved it now (requires monitoring to 100% confirmation). It seems our firewalls intrusion protection (IPS) has now started to interfere with FTP connection ignoring exceptions. Disabling the service allowed all our transfer to work smoothly again.