VPN download issue

VPN
1

I use Global Protect VPN to connect to the work. OOKLA speed test shows 180 MBPS download and 10 MBPS upload on VPN. Have no issues connecting to work, zoom & slack video calls. I am unable to download bigger size files like 200 mb from LAN to desktop. It is taking forever to download. It even takes couple of minutes to browse 5 mb file directly. I did not see these issues with Spectrum.

I have already optimized Wi-Fi MTU size to 1400.

Has anyone experienced this kind of issue? Does anyone know how to fix this issue? Thanks in advance!

Update: MTU size in my company GT profile is 1400. So, MTU size in GP profile is not the culprit in my case. Changing protocol in GP settings at my end from IPSec to SSL improved file download timing dramatically.

2

This worked for me:

3

Yeah I am noticing the same issues when downloading over a VPN for work.

4

Have you tried changing the MTU for your networking adapters or your own router to 1420?

5

Thanks for pointing me towards the fix. It did help and much better than nothing. Slow download. It took 40 min to download 400 mb file. With Spectrum, I was able to download this size of file in less than 10 min. T-Mobile Speed test results are much better than Spectrum. This download problem on VPN really sucks. Thanks again for your help!

I will dump T-Mobile once this really bothers me.

6

I am using trashcan as a router and set Wi-Fi adapter MTU to 1400.

7

Try taking your MTU down further - I convinced my GP admins to set the login profile to 1300 on their side (instead of me having to do it, when I connect the GP interface is changed dynamically) and get acceptable results. Having it set this way applies to the secondary VPN interface instead of the WiFi one which is also nice as a side effect.

GP has both an IPSec and SSL type of VPN and a full web page describing how big the packet overhead is (SSL has more overhead than IPSec, FYI) - well, you and I are also on this massive T-Mobile CGNAT which requires even more packet overhead than usual ISP stuff for other people.

My old Cisco Anyconnect SSL VPN ran OK and was set to 1340 or something like that, so we just replicated it on the GP VPN when it was set up last year and it seems to have worked out. $0.02 hope this helps.

8

ping www.google.com -f -l 1372

Got 1372 max packet size with no defragmentation. added 28 bytes for headers. I set MTU size as 1400 (1372 + 28). I see defragmentation if packet size is longer than 1372.

I will set this to 1340 and check if that improves download speed. If this does not help, I will check with our company tech people to see if they can do something at their end.

9

I dug through the subreddit archives for that link I mentioned above, here’s the previous post: https://old.reddit.com/r/tmobileisp/comments/nm9isl/globalprotect_vpn_issue_solved_for_my_situation/

Here’s the link to the GP docs from that post’s comments showing where’s configured on the GP side: Configurable Maximum Transmission Unit for GlobalProtect Connections