Slow VPN

[SunnyBerlin]

I have Red Internet & Phone 50 Cable, it works fine until I connect to my work VPN.  The connection dropps to 1 Mbps.

I've checked already the situation with company administrators and they said tht everything os ok on their side.

I've tested the connection with other internet connections (my mobile provider and in the office) and it works fine with them, so I would guess that the problem is somewhere in router or Vodafone net configuration. Can you please check it?

If you need any additional data I'll be happy to support.

Thanks.

[reneromann]

Most probably it's a misconfiguration with the maximum packet size of your company VPN that lead to many retransmissions and/or fragmented packets.

[SunnyBerlin]

why would it work good then with other internet connections?  If it's VPN issue I would expect that it shouldn't work anywhere.

[reneromann]

It depends on the MTU - the maximum size a packet can have. This size can vary - and if the size is set too big, then fragmentation may occur on links allowing only smaller packet sizes while there's no fragmentation on links that allow larger packets.

This especially happens if DualStack-Lite operation is used with IPv4 connections - in this case, the MTU is only at 1432 Byte instead of the usual 1492 or 1500 Byte. Some VPN servers detect this correctly, but others don't and need to be set up manually.

[SunnyBerlin]

I checked and unfortunatly the changes in the configuration didn't help. I found this article https://klop.solutions/dual-stack-lite-kills-mtu/ which suggest to switch the router to bridge mode. Did you try it before? Can it help?