HP NC375T Network cards

This is a followup to my slow user login post from last year. We were finally able to figure out what was going on and it turns out it was an issue with our HP/Intel NC375T network card. When in the HP system management web page and the data source was in SNMP mode the card was reporting at 1500 MTU as was everything else we looked at on the system and there were no MTU settings in the registry overriding the default MTU settings. When I switched the datasource to WBEM mode though the card started reporting that it was set at 1486 MTU. This would certainly be a problem since windows wants to send its default packets at 1500.

After much back and forth with HP and them claiming I just need to set my MTU size in the registry to 1500 under HKLM\System\CurrentControlSet\services\Tcpip\Parameters\Interfaces\ their tier 3 support was able to figure out there was a setting in the registry called "*jumbopacket" under HKLM that was set wrong. When we went into the registry this setting was set to 1500 but apparently for this card it needs to be set to 1514. I noticed that on the other card in this system it was set to 1500 and working fine though. Once this was changed and we rebooted we are now able to test ping servers using ping servername -f -l 1472 with no issues.

If you run into this issue the fix seems to be editing the registry. This setting was in multiple places in the registry all under HKLM and were all labeled *JumboPacket (yes there is a * that is not a wildcard) and the setting needed to be changed in the dword default field under the *JumboPacket key and the *JumboPacket dword field in numbered (they appear to all be numbered keys 0000 and up) keys.


1 comment:

  1. Thank you so much! Had the same issue on the HP NC375i cards after installing the driver that was shown under optional Windows Updates. Your fix outlined above fixed it.

    "netsh interface ipv4 show interfaces"
    will show what your actual MTU is according to Windows.

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