i am connecting a SUSE 11.0 Box with KDE upgraded to 4.2.1 to a PPTP Server Box which is actually a Linksys RV042 VPN Router, using “plain” PPTP Protocol. Now, independently of the encryption (40 vs. 128 bit) the connection appears extremely slow. Character response is delayed typically at least three seconds, vnc connections are basically unusable.
When i use exactly the same hardware in the same network configuration under Windows 7, the PPTP response is just fine. So i assume, that the problem in fact is somehwere in the linux box.
I am using kvpnc 0.9.0 as the frontend, pppd 2.4.4 and pptp 1.7.1.
Any hint or suggestion into which direction i could poke is highly appreciated.
Thanks you for the hint about MTU. You where exactly right in suggesting this as the troublemaker.
What i did not realize was, that KVpnc hardcodes this to 1492 by default. Lowering to 576 helped immediately. So whenever you are around Vienna, call for a beer
A little hint for people reading this thread later:
To get an idea about the correct MTU one can use a little trick.
The program “ping” allows you to
a) send packages of a certain size
b) discover the MTU when sending a packet, which certainly will be too big, because the packet will be fragmented to the MTU-size.
ping -c 1 -s <Size> -M do <some address or IP>
Example:
A use “normal” ethernet which has an MTU of 1500, so 1600 will certainly be too big (Note: There are also 28 bytes added to the size you give to ping via the “-s” switch, resembling the package header AFAIK.)
ping -c 1 -s 1572 -M do opensuse.org
PING opensuse.org (130.57.5.70) 1572(1600) bytes of data.
From ******** (XX.XX.XX.XX) icmp_seq=1
**Frag needed and DF set (mtu = 1500)**
--- opensuse.org ping statistics ---
0 packets transmitted, 0 received, +1 errors
i followed your lead and learned it starts working smoothly here at
1472, so i googled around and used this magic:
ifconfig eth0 mtu 1472
voilà!!
i shut down the box overnight and today, voilà it is back to the 1500
default <sigh>…
how does one make that persist through reboot (using eth0 through a
firewal/router to a *DLS modem) please (i ask as i admit i’m too
stupid to find the magic search sequence to force google to tell me!)??
THANK YOU, my /etc/sysconfig/network/ifcfg-eth0 includes: MTU=‘1472’
but while waiting for a reply i did some more google and found this
GUI path (in v10.3 w/KDE3) which i record here for those who can’t yet
figure out that ‘scary’ CLI:
YaST > root pass > Network Devices > Network Card > Overview (tab) >
Configure > General (tab) and change/fill in the MTU blank with the
magic number, then Finish
