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Author Topic: F/W 1.11 - Fibre 400/200: MTU Setting  (Read 772 times)

hilaireg

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F/W 1.11 - Fibre 400/200: MTU Setting
« on: July 02, 2020, 06:14:23 AM »

Hi All,

Anyone noticed that the MTU setting for the DIR-3040 is restricted to a range 1280-1492 when using a PPPoE account over Fibre?  Typically, 1492 should be fine but I've been reading of late that the recommendation is to set the MTU to 1500 when using PPPoE on a Fibre connection as the 8 byte overhead has factored in already - i.e. 1508 MTU.

I'm experiencing occasional "stalls" when downloading from slow hosts (ex: SendSpace, FileFactory, etc.) as well as interment errors loading "www.google.com" throughout the day.  I've tested on numerous devices that I own and the issue seems to be consistent - MacOS/WinOS.  ISP (Vianet) speedtests return desired results.  I've ruled out the internal network switch (DELL PowerConnect 2848) as the logging on the ports show ZERO dropped packets or errors - i.e. logging is clean.

I started noticing the issue back when I did the last f/w update and now that the issue is still present with f/w 1.11, I'm trying to pinpoint what might be the root cause.  Restarting the ISP equipment and my network equipment doesn't seem to make a difference.

I'd appreciate some insight from anyone using a PPPoE account over Fibre and/or any other suggestions as to what I could look at.

Cheers,
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GreenBay42

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #1 on: July 02, 2020, 07:45:33 AM »

You may want to connect a PC directly and play with the MTU settings on your ethernet adapter to test.

Have you contacted Vianet to see what the optimal MTU setting is?

You may want to contact D-Link Canada tech support to report the issue. They can send a ticket to the engineers to see if it is possible to increase the MTU above 1492.
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FurryNutz

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #2 on: July 02, 2020, 10:12:26 AM »

Max MTU value should be 1500. So 1492 with the 8 byte count would out the MTU at 1500 which would be standard. You can't have a MTU value of anything over 1500.
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Cable: 1Gb/50Mb>NetGear CAX80>DIR-882>HP 24pt Gb Switch. COVR-1202/2202/3902,DIR-2660/80,3xDGL-4500s,DIR-857,835,827,815,890L,880L,868L,836L,810L,685,657,3x655s,645,628,601,DNR-202L,DNS-345,DCS-933L,936L,960L and 8000LH.

hilaireg

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #3 on: July 02, 2020, 12:48:13 PM »

Max MTU value should be 1500. So 1492 with the 8 byte count would out the MTU at 1500 which would be standard. You can't have a MTU value of anything over 1500.

From what I'm gathering, many Fibre-based services are pre-processing the MTU on "their side".  So, does that imply that the MTU is "coming in" at 1492 ?  Does it further imply that an MTU of 1492 on the DIR is further reducing the size - i.e. ISP MTU (1492) & DIR MTU (1492) = MTU (1484) ?  Would that suggest that the MTU in the DIR should be set to 1484 or 1500 ? 

Not sure, hence the inquiry ... and could likely be a moot point. 

Which brings me back to my being open to suggestions on what else to trace (look for) to try and pinpoint why downloads from low-speed hosting services (Sendspace, FileFactor, RapidGator, etc.) all stall-out in the last MB of download.

Thoughts?
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FurryNutz

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #4 on: July 02, 2020, 01:15:01 PM »

You'll need to ask the ISP what there processing for MTU. Most D-Link routers and other routers operate at a default value of 1500. Some mfrs allow users to change the MTU value to something lower. Like for DSL and PPPOE which usually operate at 1472 or 1492. Again, this is something to ask the ISP on what they support and what is needed.
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Cable: 1Gb/50Mb>NetGear CAX80>DIR-882>HP 24pt Gb Switch. COVR-1202/2202/3902,DIR-2660/80,3xDGL-4500s,DIR-857,835,827,815,890L,880L,868L,836L,810L,685,657,3x655s,645,628,601,DNR-202L,DNS-345,DCS-933L,936L,960L and 8000LH.

hilaireg

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #5 on: July 02, 2020, 04:40:06 PM »

Did the "old school" ping test (ping www.yahoo.com -f -l 1464) to confirm the MTU value on the DIR and added the IP/ICMP headers (28 bytes) to the value which results in 1492.  That rules out a "sliding" MTU as being the issue.

Changed the DNS to CloudFlare/Google to rule out DNS.


Ref:
https://en.wikipedia.org/wiki/Ping_(networking_utility)
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FurryNutz

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #6 on: July 02, 2020, 04:47:24 PM »

 ;)
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Cable: 1Gb/50Mb>NetGear CAX80>DIR-882>HP 24pt Gb Switch. COVR-1202/2202/3902,DIR-2660/80,3xDGL-4500s,DIR-857,835,827,815,890L,880L,868L,836L,810L,685,657,3x655s,645,628,601,DNR-202L,DNS-345,DCS-933L,936L,960L and 8000LH.

hilaireg

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #7 on: July 12, 2020, 08:04:17 PM »

Disabled "Energy Efficient Ethernet" on the switch; that seems to have made a noticeable improvement on macOS and winOS - i.e. haven't seen the intermittent DNS resolve issues or the low-speed hosting services (Sendspace, FileFactor, RapidGator, etc.) stall-outs in the last MB of download.
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FurryNutz

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Re: F/W 1.11 - Fibre 400/200: MTU Setting
« Reply #8 on: July 13, 2020, 10:54:06 AM »

That feature seems to cause problems from what I've seen.
Thanks for letting us know.
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Cable: 1Gb/50Mb>NetGear CAX80>DIR-882>HP 24pt Gb Switch. COVR-1202/2202/3902,DIR-2660/80,3xDGL-4500s,DIR-857,835,827,815,890L,880L,868L,836L,810L,685,657,3x655s,645,628,601,DNR-202L,DNS-345,DCS-933L,936L,960L and 8000LH.