MTU pinging with random request timed out

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Jgalz9

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Wannabe Geek

#111929 20-Nov-2012 00:29

Hi guys,
I really hope someone can help as this has been an issue for months. I am generally inexperienced with setting up wireless routers etc but at home our service provider is Telstraclear (yay...) and we have a cable modem which always runs fine when directly connected to a pc. Months ago I setup a D-link Dir-615 wireless modem/router from the cable modem which after a lot of stuffing around eventually worked..ish. It dropped its connection at times and got worse so I decided to reboot it and try again. Now we are all up and running with majority of website except for ones such as yahoo or gmail.
This happened last time and it was an MTU issue so i I once again used the "ping yahoo.com -f -l xxxx" going down in 10s but all I seem to either get is four request times out, or random replies with a couple moe request timed out.
Does ANYBODY know what Ive done wrong? Maybe theres a setting I havent quite got right?

Pleeeeease help me, I have battled on and on to no avail!

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Snowflake

#719861 20-Nov-2012 00:58

is your cable modem running pppoe? try setting the MTU on the dlink, and on your client pc's to something smaller than 1480. the default on your dlink will be 1500 which is too big when you have pppoe.

How to change the PPPoE MTU size in Windows XP
http://support.microsoft.com/kb/283165

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sbiddle

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#719873 20-Nov-2012 06:16

First off I'm not sure why you would be touching the MTU. TelstraClear use static IP's with a MTU of 1500 which is the default for every Ethernet device out there.

Change it back to 1500 and things should be fine.

Jgalz9

10 posts

Wannabe Geek

#719890 20-Nov-2012 07:52

I am not currenty running pppoe as I was told that this did not apply for cable. I can edit MTU size on the wireless router but have dropped it down to 1300 but some site still dont work. I remember last time changing the MTU eventually got things going but this is when the connection began to drop off.

Jgalz9

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Wannabe Geek

#719891 20-Nov-2012 07:53

I set up the router as a static IP as this I what I thought it was under.

sbiddle

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#719900 20-Nov-2012 08:15

Jgalz9: I am not currenty running pppoe as I was told that this did not apply for cable. I can edit MTU size on the wireless router but have dropped it down to 1300 but some site still dont work. I remember last time changing the MTU eventually got things going but this is when the connection began to drop off.

MTU isn't something you play with, you set it to what your ISP supports

As I posted above TelstraClear use the stock standard Ethernet MTU of 1500. This is the default for all Ethernet routers. Set it back to this and your problems will be solved.

Jgalz9

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Wannabe Geek

#719904 20-Nov-2012 08:31

Hey thats what I thought too. I have changed it back to default but a couple site such as gmail still don't work? Next step haha fml

theEd

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#719913 20-Nov-2012 08:49

sbiddle: MTU isn't something you play with, you set it to what your ISP supports

As I posted above TelstraClear use the stock standard Ethernet MTU of 1500. This is the default for all Ethernet routers. Set it back to this and your problems will be solved.

I've had quite a few calls lately from people asking how to change MTU on their DrayTeks, apparently the TelstraClear helpdesk is suggesting people lower their MTU as a troubleshooting step now... and apparently most of the time it does fix things. So something seriously funky is going on with their network.

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sbiddle

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#719915 20-Nov-2012 08:54

theEd:
sbiddle: MTU isn't something you play with, you set it to what your ISP supports

As I posted above TelstraClear use the stock standard Ethernet MTU of 1500. This is the default for all Ethernet routers. Set it back to this and your problems will be solved.

I've had quite a few calls lately from people asking how to change MTU on their DrayTeks, apparently the TelstraClear helpdesk is suggesting people lower their MTU as a troubleshooting step now... and apparently most of the time it does fix things. So something seriously funky is going on with their network.

Is this DSL or cable?

Jgalz9

10 posts

Wannabe Geek

#719930 20-Nov-2012 09:18

This is a cable connection. It seems to have trouble with sites that are secure e.g. Gmail hotmail and some banking sites. I've called telstraclear helpdesk and he assures me it's nothing to do with MTU but who knows. When I try any ping any sites though, even ones I can access easily it still times out the majority of requests with the odd reply

Jgalz9

10 posts

Wannabe Geek

#719933 20-Nov-2012 09:19

Wirelessly pinging back to router works fine though

Jgalz9

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Wannabe Geek

#719942 20-Nov-2012 09:36

Ok update so I unabled SPI (stateful packet inspection) and changed the NAT endpoint filtering endpoint independent and now it seems to work? This was all done on firewall settings, will it still be safe and secure?

theEd

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#719965 20-Nov-2012 10:22

sbiddle: Is this DSL or cable?

Have had it asked about the 120 (ADSL), 2750 (VDSL) and 2130 (Ethernet WAN), so they're suggesting it for all three. I think it's mostly their ADSL that benefits from having it lowered though.

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Snowflake

#720039 20-Nov-2012 12:39

sbiddle: First off I'm not sure why you would be touching the MTU. TelstraClear use static IP's with a MTU of 1500 which is the default for every Ethernet device out there.

Change it back to 1500 and things should be fine.

yep. if you're not running PPPOE then you really shouldn't need to mess with it

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Jgalz9

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Wannabe Geek

#720041 20-Nov-2012 12:41

I see, so as it stands I have disabled the SPI setting in the firewall and it seems to be fine now, but we are back to the initial problem of connection dropping off randomly. Everything pings fine now too! But connection to the router drops 4 to five times a day and only can be fixed by resetting both the wireless and cable router. Any ideas?

Regs

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Snowflake

#720042 20-Nov-2012 12:44

Jgalz9: Ok update so I unabled SPI (stateful packet inspection) and changed the NAT endpoint filtering endpoint independent and now it seems to work? This was all done on firewall settings, will it still be safe and secure?

if you are not punching hole in your router to run a web server or a bit torrent client (for example) then you will pretty much be fine with plain old NAT. (you're more likely to fall victim to a vulnerability in a website that traverses the firewall/router regardless of SPI settings)

SPI and filtering will definitely mess with your traffic and cause issues like you're seeing. they are advanced features which you probably should leave alone if you don't know how to configure them.

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