do NVIDIA NICs support MTU > 1500?

[plonk420]

after maxing out data transfer rates from this computer at "merely" 40MB/sec, some people advised me to try jumbo MTU frames. after successfully setting a less important Vista system to an MTU of 5000 via the command line, and a Windows 7 system via an option on the NIC properties and verifying there were no communications issues, i went about setting my main computer to the same.

then nothing worked. i could only ping localhost.

diagnose and repair didn't help. actually seemed like i couldn't enable the Local Area Connection (could have been that i'd started a diagnostic in a separate window). **edit: see post 9 in this thread (08:59 PM)**

anywho, gave up, set MTU back to 1500, rebooted. everything working perfectly.

while waiting for this computer to reboot all those times/diagnose and repair, i did a test transfer between the 2 computers i COULD set the MTU to 5000 on and i got 60-80MB/sec.

anyone else have any experiences with this?

not working: K9N2GM (-FD?) nic: RTL8211BL
working: M2A-VM nic: RTL8168B/8111B Family (according to Vista)
working: P5K SE/EPU nic: Atheros L1 (according to Windows 7; Asus's site was useless)

 

[Crusty]

What switch do you have?

 

[plonk420]

netgear gs105

 

[Crusty]

Well the switch does support jumbo frames so that's not the problem.

Are you sure the RTL8211BL nic is connecting at 1gbps? There's been problems with nvidia nics not being able to auto-negotiate 1gbps. Check the networking tab in Task Manager to see the link speed.

 

[plonk420]

definitely connecting at 1gbps. can't get 40, or even 20MB/sec on 100mbit (12.5MB not counting tcp/ip overhead, which i have no idea anything about)

edit: L.A.C. Status: Speed 1.0 Gbps

 

[Crusty]

Is it at 1gbps when you have your MTU up at 5k? I thought it didn't work at all when it was set there.

 

[plonk420]

the local area connection becomes disabled when MTU is up at 5K

edit: i'm mostly but not 100% certain of the correlation between the two.

 

[Crusty]

As in the control panel says 'Disabled' under the NIC? Or does it say Cable Unplugged?

If it really just says 'Disabled' have you tried to 'Enable' it by right clicking on it and selecting Enable?

 

[plonk420]

it wouldn't enable. it would just sit there. or rather, i gave up after 10 minutes of it sitting there.

edit: i take that back about the local area connection being disabled. it must have gotten that way from "diagnose and repair" possibly trying to disable it then reenable it.

i did it again. the L.A.C. is enabled, 1 Gbps. i see "a connection" on the switch. still can't ping anything except for localhost.

set MTU to 1500, reboot, everything's fixed.

 

[Crusty]

What's the output of ipconfig /all when you set the MTU to 5000?

If you are using a DHCP address you might want to try setting a static IP address with the correct informatin.

 

[plonk420]

anything in particular you need/are looking for?

edit: my pfsense box assigns IP by mac address. traffic more or less doesn't hit the router, tho.

edit2: box has proper ip address (192.*), just can't ping ANYTHING on the network; other comptuers, router, modem, google by ip.

 

[Crusty]

Yes, I'm trying to make sure your computer is actually getting an IP address. Is your pfsense box running gigabit too? You can't run jumbo frames if you have clients that are running 100mbps on your LAN.

 

[plonk420]

actually, no. there's a 100mbit switch between the pfsense box and the gbit switch, tho. however, if the OSes are doing their job, it's not even touching the pfsense box (or if so, just to figure out the ip address of the other boxes).

all of the computers connecting to each other have gbit and pass thru the gbit switch. all 3 are connected on the same switch. the two others can surf, communicate with each other just fine.

the problem computer is 192.168.1.10 and it's an IP address that i have my pfsense box assign it via its mac. and i can't ping the pfsense box, either. (pfsense is 192.168.1.1; modem from the inside is 192.168.100.1)

there's another (possibly unnecessary) 100mbit switch up the line*, but none of this data (or a minimal amount at least), should, in theory, travel thru it. i'd consider the switch a moot point as the other computers work just fine. the nonworking computer (as well as ALL of the computers) are set to DHCP. if i wish to force an IP, i do it from the pfsense box. oh, since we're on the subject, all *3* computers are forced IP addresses by pfsense.

*for PS3 and eventually for a throttled WAP.


edit: wording

edit 2: this is the computer in question, so, if i sound hesitant to take it out of commission, that is why

edit 3: wording, added first paragraph.

 

[Madwand1]

Yes, some nVIDIA NICs support jumbo frames, but not all of them do, and even nVIDIA Support can't correctly tell which ones do or don't.

Just go into the NIC advanced properties, and see if you have an option to set jumbo frame size or something like that. If you do, then the NIC supports it, otherwise it doesn't. In theory there could be just a driver problem. In practice, you probably couldn't fix this without also fixing the driver.

Jumbo frames also aren't generally a magic bullet, and there could be other things to try instead. E.g. changing the "Optimize For" setting.

Also see what your NIC's performance is like without factoring in the drives, e.g. using iperf.

 

[plonk420]

thanks! i'll look into that.

during this troubleshooting, a friend says that he gets 60-80MB/sec without having to set jumbo frames (not sure his mobo or nic chipset). i'll see if i can figure out Java etc...

 

[plonk420]

hmm... odd, i get 920mbps with iperf (with 4 or more threads), 880mbps (with 3). still, i'm supposed to get ~78MB/sec (650mbps) with 2.

i guess the bottleneck is maybe the file I/O system? yay vista!

edit: wait, that still doesn't answer why i can get more between 2 other computers with MTU 5000. ah well. at least the system is CAPABLE of it...