Problem changing interface MTU on windows server 2003
Posted on 2009-02-18
My current network diagram is,
WEB SERVER <--> MIKROTIK ROUTER <--> ADSL MODEM <--> INTERNET
I'm having connection problem when accessing my web server from the internet, looks like the connection only transferred a portion of the webpage and suddenly disconnects it.
I've tried troubleshooting it, and narrows it to the web server's MTU problem.
Wireshark shows multiple ICMP (FRAGMENTATION NEEDED) from the ADSL modem to the server stating that the next hop MTU is 1432. (this means that ICMP is not being blocked by the firewall)
But my web server is still sending oversized packets, sized 2704 bytes and continously being dropped.
The first time i thought this was because of the dual NAT-ing, ADSL & Mikrotik. I tried lowering the public interface in mikrotik to 1400, but now the ICMP (fragmentation needed) comes from the router not from the modem and STILL my web server tries to resend 2704 bytes packets.
I've also tried manually lowering the MTU using the registry keys founded here,
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<ID for network interface>
but wireshark shows that my server still sends 2704 bytes packets. Looks like changing the registry key have no effects at all.
I'm using an intel server motherboard,
the onboard nic is an "Intel(R) PRO/1000 EB Network Connection with I/O Acceleration"
I've tried updating the driver to the latest version, and still no success.