Deterministic Network Enhancer Problem (?)

j-winder · ‎07-18-2002

Hello,

I am in Japan trying to set up a VPN using a PPPOE based connection called "BFlets".

However, when VPN Dialer is installed and Deterministic Network Enhancer kicks in, the computer becomes unable to ping large packets, and therefore unable to transfer files on the VPN. It simply freezes during file transfer.

Example :

C:\>ping -t -l 2048 -w 4000 210.81.11.82

Pinging 210.81.11.82 with 2048 bytes of data:

Request timed out.

BUT, If I unbind the Deterministic Network Enhancer on the Intel Pro100 NIC, it works fine, and I can ping with large packets and the VPN works perfectly. Until the computer is rebooted. Then it doesnt work at all - it cannot even connect to the internet.

I then have to re-bind and reboot, and the original problem with large packets dropping happens again.

Also, the connection software creates a virtual PPPOE Network Adapter that is also bound to the D.N.E. Im not sure if this could be causing difficulties.

This problem is quite frustrating, so I would really appreciate any help or advice on this. Im sure people must have used BFlets with VPN's in Japan before.

Thankyou very much for your time and help!

Jason

paqiu · ‎07-19-2002

Hi Jason,

It is a MTU issue. IPSEC put more than 60- 80 bytes extra IP header, so the MTU need to be low down to 1420 (for VPN client). PPPoE put extral 8 bytes ip header as well. so 1400 for PPPoE should be fine.

VPN client itself has a program called "SETMTU".

You can use that to set the normal local network and dial-up connection MTU size.

Most of the time, you do not need to manually set MTU, because the MTU of the local network adpater has been set to 1400 when Ciso VPN client installed.

But most of the time, set MTU will not work to PPPoE connection. Because PPPoE installed another virtual Adapter , VPN client can not adjust MTU for that adpter.

Please talk to your service provider. Most of the PPPoE ISP has their own programs to change MTU for their virtual adapter ( A few does not have special program need to modify the windows 2000 registry).

Please set the MTU to 1400 or 1380, then it should be working fine.

Please check following URL for change MTU for PPPoE:

http://www.cisco.com/warp/public/794/router_mtu.html

Best Regards,