Problem with Jumbo Frames

I am trying to set up jumbo frames on my gigabit home LAN but no luck so far.

My setup is:

* D-Link DIR-655 router, HW Revision A3, Firmware 1.21 EU
* Synology DS107+, Firmware 3.0-1337
* Laptop w/ Win7 x64, external PCIx NIC managed by "Generic Marvel Yukon 88E8053 based Ethernet Controller"

The router is supposed to support jumbo frames but doesn't feature any relevant setting. I set the Jumbo Packet value to 9000 on both the NIC and the Synobox but it doesn't work, ping -f -l 8972 says "Packet needs to be fragmented but DF set".

Is there any other setting I overlooked, the DIR-655 doesn't actually support jumbo frames, or what else could be the problem?

Spookyone

Posted 2010-10-07T22:21:42.023

Reputation: 31

Jumbo frames mean just that, layer-2 frames. A router will strip off a frame header before routing, and the packet is what gets routed. The packet needs to conform to the minimum MTU along the path, else it needs to be fragmented. The jumbo frames are probably supported on the switch part of your device, but trying to route large packets across the Internet will not be supported. – Ron Maupin – 2016-07-25T21:41:22.577

Answers

I can find no reference in the manual or specifications that is supports an MTU of over 1500. In fact, the inside side of that router doesn't seem to have any MTU settings at all. Only the ISP facing side has those settings and there is no indication that it supports large values.

That device most probably does not support jumbo frames.

SysAdmin1138

Posted 2010-10-07T22:21:42.023

Reputation: 5 239

You can try gradually raising the packet size until it stops working. I've seen equipment "supporting" jumbo frames with jumbo meaning 4k or 6k bytes max.

knitti

Posted 2010-10-07T22:21:42.023

Reputation: 871

A good point. The ProCURVE switch I have access to has two settings for Jumbo Frames, 4K and 8K. – SysAdmin1138 – 2010-10-08T01:58:26.267

I have this router and can confirm after manually setting 4k jumbo frame sizes on both router and network cards, jumbo frames worked correctly.

IrqJD

Posted 2010-10-07T22:21:42.023

Reputation: 186