I'm hoping for a pointer!

I have a FTP server behind my Vigor 3900, NATed to a static public IP - no bandwith limitations set up or enabled at all.

If I transfer, say, a single 1GB file to or from the FTP server from a client on an external IP, via the static Public IP, I get a max throughput of around 5 mb/s.

However, if I transfer, the same file to or from the FTP server from a client on an internal IP, via the static Public IP, I get a max throughput of around 60 mb/s.

The broadband connection to the Vigor is 145mb down, 45mb up - the connection at the client is 15mb down, 16mb up.

Is there a default of 5mb/s per connection in play here somewhere? I can find nothing to suggest there is, but am stumped as to the cause of the speed limit in both directions.

Any help would be gratefully appreciated.

Could this be throttling by the ISP?

I've done it many times before so I thought I'd mention but are you sure you're not accidentally confusing metrics?

"The broadband connection to the Vigor is 145mb down, 45mb up - the connection at the client is 15mb down, 16mb up."

It doesn't explain the issue if it's happening in both directions but the FTP server providing files will be limited by the upload - 45 megabit per second will roughly translate to 5 megabyte per second for any external clients (assuming they can reach those download speeds)

Hi, I acknowledge the odd numbers on speeds but these are Speed Test speeds rather than those posted by the ISP. The issue is in both directions and appears limited only to access to the FTP server behind the firewall (ie if i try to download a large file from, say DropBox online, from inside the firewall it transfers in no time at all).

I have tried the same thing from our other office, which also has a high speed internet fibre connection, this time provided by a different supplier and also can only get a max 5mb/s speed when transferring to or from the FTP server (if I try it using the high speed LAN-LAN fibre we have connecting the two offices, it's 60mb/s or so)

hornbyp wrote:
Could this be throttling by the ISP?

Being that it only seem to affect this FTP traffic (as far as I can tell) can the ISP be this specific?

riprap wrote:
Being that it only seem to affect this FTP traffic (as far as I can tell) can the ISP be this specific?

Yes, they could throttle it by Port Number. Whether they do or not is another matter; I would hope they'd acknowledge the fact, if they are. (Are the client and Server using the same ISP, or are there two ISP's to consider?)