openvpn: new client - slow connection, same config - why??


I use openvpn to tunnel my internet traffic over linode. for years it worked with 15mbit (i´m far away from my linode :).

recently i changed internet subscription from 20mbps docsis to 55mbps docsis - same provider, new modem (technicolor), didnt realize it changed a thing, apart that the line has 55mbps with direct connections.

then my win7 client crashed.

re-installed win7, installed openvpn, using old config.

now openvpn is max 5mbps, with the old client it was approx. 15 mbit.

plz help me debug this, i dont see the problem…

here´s the client config

proto udp
ns-cert-type server 
dev-node tap
remote x.x.x.x 32799
ca xx.crt
cert xxx.crt
key xxxx.key

server config is

port 32799 
proto udp
dev tap0
ca xxx.crt
cert xxxx.crt
key xxxx.key
dh dh512.pem
keepalive 10 120
push "redirect-gateway def1 bypass-dhcp"
push "redirect-gateway def1"
push "dhcp-option DNS"
push "route"
max-clients 25
status /var/log/openvpn.log
verb 4

1 Reply


i did some testing and nothing changed, until i connected to the openvpn server using a macbook on another internet line, and voila - 13mbit downstream.

so i let the technician check my internet line. he changed the modem to a new one, but same product (technicolor 7200). same dismal speed of 2-4 mbit.

now i did some testing using "netalyzr" ( while the openvpn tunnel was up and it says:

"you cannot send fragmented udp traffic, fragmented udp traffic could be received. your modem or firewall seems not be capable of handling udp fragmentation. the biggest sent udp packet was 1383 bytes". another test says that the biggest udp packet was 1393.

could it be that i have a fragmentatin issue?

i now tried setting

tun-mtu 1383


tun-mtu 1393

or even

tun-mtu 1333

on server and client but nothing changed..

how do i have to handle this fragmentation issue?



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