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Author Topic: DIR-655 used as gigabit switch and Wi-Fi AP: can I set DIR-655 MTU to 9000?  (Read 8755 times)

bripab007

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So, I'm using a 10/100 WRT54G running Tomato firmware as my firwall/NAT, handing out static DHCP to all devices, doing all port fowarding, and Wi-Fi turned off.

I have my DIR-655 connected to the WRT54G via patch cable, have turned off all DHCP and firewalling/NAT functions on it and have the Wi-Fi access point turned on.

Patched into the DIR-655, I have two 1000Mbit devices that both have jumbo frames capability enabled and both have MTU set to 9000.  I also have one device on the DIR-655 switch that's only a 100Mbit connection.

I guess my question is, what affects, adverse or otherwise, would I encounter if I cranked up the MTU setting in the DIR-655 to 9000?

Would my two 1000Mbit devices transfer files to one another more quickly than they are now?  Would the 100Mbit device suffer packet loss or other issues when transferring files from one of these 1000Mbit devices?
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Sammydad1

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Hi,

MTU is somewhat of a universal thing over the net with the max setting at 1500....  I have seen some sites not open properly if the MTU setting locally was out of synch by too much.

SD1
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DIR-655 A2, FW: 1.35NA

Lycan

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  • Posts: 5335

Ideally the switch in the 655 should negotiate connection MTU between clients, but 9K is a large frame.
I'd run it that way and clock transfers, see what happens.
What are you ohoping to achieve?
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bripab007

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I dunno, same thing anyone's trying to achieve with jumbo frames:  faster transfer speeds of large files.

The two 1000Mbit devices on that switch are a DNS-323 which servers my music and video libraries to my computer (the other 1000Mbit device, which runes iTunes interface directly off a DNS-323 network share) and my 100Mbit connection Xbox running XBMC dashboard.

I pretty much enabled jumbo frames on both my PC gigabit NIC and DNS-323 the same day, so I have no frame of reference for jumbo frames/not jumbo frames.  I can tell you that the PC definitely transfers files much faster to an iPod than it did before with my old 100Mbit Linksys NSLU2 and 100Mbit NIC in the PC.  Backup jobs from the PC to the DNS-323 are also much faster.
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Lycan

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Those faster transfer times dnot mean that the jumbo frames are really helping.
I'd disable them and see if the speeds decrease.
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bripab007

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  • Posts: 104

Right.  That's exactly why I mentioned the fact that I enabled jumbo frames immediately upon installing the gigabit NIC in the PC as well as the DNS-323.  Probably should've waited.

Like I said, I'm seeing better transfer rates already between the DNS-323 and the PC vs. the prior NSLU2 and PC, but that's just due to being connected at 1000Mbit rather than 100Mbit.  Hell, even XBMC on the Xbox was loading my pictures/photos network share faster than it did from the NSLU2, so that tells me the NSLU2 was probably bottlenecked at its processor or something.

Yeah, I think I'll disable jumbo frames and just sorta see how it runs for a while.  Any recommendations on free/open-source network transfer speed clocking utilities?
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