OpenVPN slow down after switch change

AndyM

I experience very weird problem with OpenVPN. I use it to connect to my office network. Office network includes two machines. OpenVPN server is installed on Machine #1 and there are no problems with it. Also I need to access to Machine #2 which is in the same network and connected with Machine #1 throught Trendnet gigabit switch. The problem has begun when switch has been broken and I replaced it to another one (also Trendnet - I think it does not matter). After that communication with Machine #2 through OpenVPN became very slow and unstable. When I ping it with large packets - there is 10-20% packet loss. I started playing with "fragment" parameter. When I set it to 900 or smaller - packet losses disappear. But the connection to Machine is still very slow. In all cases connection to Machine #1 is fine. Is there any ideas ?

My configuration files are as follows:

Server:

local x.x.x.x
port 1194
proto udp
dev tun
dev-node OpenVPN_Srv

ca ca.crt
cert xxx.crt
key xxx.key
dh dh1024.pem

server 10.111.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt

push "route 10.111.0.0 255.255.255.0"
push "route x.x.x.x 255.255.255.0"
push "dhcp-option DNS x.x.x.x"

client-config-dir "c:\\Program Files (x86)\\OpenVPN\\config\\ccd"

keepalive 10 60

comp-lzo

persist-key
persist-tun

log-append  openvpn.log

verb 4

mssfix
fragment 1200

Client:

client
dev tun
proto udp

remote x.x.x.x 1194
resolv-retry infinite

nobind

persist-key
persist-tun

ca ca.crt
cert xxx.crt
key xxx.key

ns-cert-type server

comp-lzo

verb 3

route-method exe
route-delay 10

mssfix 
fragment 1200

maikcat

hi there,

because you mentioned the switch swap...

if you try from your lan to connect to your openvpn server via
any protocol you want (rdp,smb) is it working ok?
do you have any packet loss inside your lan?

what if you try to set ethernet adapter speed manual (10 half f.e)
does it change anything..?

Michael.

ps: the push route line inside your server config that reffers to openvpn tun not necessary
>push "route 10.111.0.0 255.255.255.0"

AndyM

Thank you for your answer !

Everything is OK via LAN. No packet losses, RDP and SMB work OK.

I changed network speed on Machine #2 to 100 Mbit - no effect.

maikcat

if you think its MTU problem you ca do the following:

--copied from another post by user janjust

1) determine the optimal MTU value; this can be done by pinging the server using
Code:
ping -M do -s <size> server

on linux or using
Code:
ping -f -l <size> server

on Windows; vary <size> to find the optimal value; I'd start out with 1472 , as that is the default for ethernet networks.
If the MTU needs to be lowered then lower it on both ends

Michael.

AndyM

MTU on LAN is 1472. I tried to change tun-mtu and link-mtu to lower values without any success.

I connected to my network via PPTP and there are no problems.

AndyM

The problem is resolved. When I replaced the switch I did not turn off the router which connects to Internet. All OpenVPN packets went through that router. Possibly router did not read new switch hardware parameters. When I rebooted the router - problem has gone.

maikcat

ok then

closing topic.

Michael.