How To Increase A D S L Router's Mtu Setting

[JetsetBkk]

I've been having a problem with Internet Banking for about a month.

My bank is Nationwide in the UK and two functions stopped working in mid-December: the ability to transfer money to another bank in the UK and the ability to send long messages to the support people at Nationwide.

I have eventually got an intelligent response from one of the support guys who admits that other customers have had the same problems. His response states that the MTU [Maximum Transmission Unit, TCP/IP] of my ADSL router is too low, meaning that it doesn't send a complete message or packet back to the web site:

This problem is found to affect customers who connect to the Internet via an ADSL router, rather than an ADSL modem. Even if you are not aware of any changes to your router settings this can be reset by your provider remotely. Once checked and amended as below this should resolve the problem.

Some ADSL routers do not correctly send large packets of data (over 1200 to 1420 bytes) from the locally connected PC to the Internet Service Provider (ISP).

On most routers there is an MTU setting which can be manually adjusted which, if set correctly, will resolve this issue. Nationwide recommends setting your MTU value on your ZyXEL Prestige 660R-61C router to either 1420 or 1200 bytes, see which works best. For customers using ADSL routers where this setting is not visible/available, you may be required to upgrade the firmware of the router from the manufacturer.

The problem is that the ZyXEL router does not have an MTU setting that I can find.

So, has anyone else had a problem like this and have a solution, because I'm really not looking forward to trying to explain this to Maxnet.

[Katoey]

Most ADSL routers set the MTU value at 1492 and there is no need to change that value normally.

Things you should do if you have WinXP Home/Pro SP2:

Run this program (address below) to increase your TCP max connections from 10 to 50.

Download "EvID4226Patch223d-en.zip" EventID 4226 Patcher Version 2.23d (english) from:

http://www.lvllord.de/?lang=en&url=downloads#4226patch

You can run "TCP Optimizer" to tweak you router.

Download from: http://www.speedguide.net/downloads.php

Documentation from: http://www.speedguide.net/tcpoptimizer.php

TCP Optimizer will display your current router setings and you can tweak them if you wish.

Hope this helps you.

Edited January 18, 2008 by Katoey

[JetsetBkk]

Most ADSL routers set the MTU value at 1492 and there is no need to change that value normally.

Things you should do if you have WinXP Home/Pro SP2:

Run this program (address below) to increase your TCP max connections from 10 to 50.

Download "EvID4226Patch223d-en.zip" EventID 4226 Patcher Version 2.23d (english) from:

http://www.lvllord.de/?lang=en&url=downloads#4226patch

You can run "TCP Optimizer" to tweak you router.

Download from: http://www.speedguide.net/downloads.php

Documentation from: http://www.speedguide.net/tcpoptimizer.php

TCP Optimizer will display your current router setings and you can tweak them if you wish.

Hope this helps you.

Thanks for your reply. I have been to that LvlLord's web site before, a long time ago. But then I didn't do anything about patching TCPIP.sys as I didn't have any event ID's no. 4226. Strangely, I have a few now, so I will give it a go.

Regarding "TCP Optimizer", I've read elsewhere about the registry setting for the "EnablePMTUDiscovery" DWORD and was thinking of changing that, so it's interesting that the tweaker you suggest does the same.

So, first of all I'm going to back up my HD and then give them a go!

[Prasert]

If mtu 1492 doesn't work for you try 1452.

Problems with mtu sizes are known for the Alcatel Fox DSLAMs (in use by TOT and TT&T) when using PPPoE.

[JetsetBkk]

If mtu 1492 doesn't work for you try 1452.

Problems with mtu sizes are known for the Alcatel Fox DSLAMs (in use by TOT and TT&T) when using PPPoE.

Thanks for that - I did the ID4226 patch and the tweaks that "TCP Optimizer" from Speedguide.net suggested. One of those tweaks was to set the MTU to 1492 after I did the "Largest MTU" test. But after doing that and rebooting, there was no change with the problem at the Nationwide site.

I did do a speed test using Speedtest.net and got the best result I've ever had to Bangkok - about 2350 kbps, but that may just have been a coincidence.

I'll give 1452 MTU size a go...

[JetsetBkk]

If mtu 1492 doesn't work for you try 1452.

Problems with mtu sizes are known for the Alcatel Fox DSLAMs (in use by TOT and TT&T) when using PPPoE.

Thank you Prasert!! If I ever go to Koh Tao I'll buy you a drink, or ten. At last, after weeks of trying, my banking site is working normally! I tried an MTU of 1452, but it didn't work, so I decided to cut it drastically and changed it to 1200 - and it worked! What a relief!

I then changed it back up to 1400 and it's still working, so - as you say - the equipment at TT&T doesn't like a big MTU value. I'll play around some more to see what the maximum is, and then set it back by 32 or so as a safety margin.

I can only guess that TT&T have done some equipment or configuration changes at the exchange (central office) and have caused this problem because I can't think what I could have done to cause this.

Thanks again for your help. Bl00dy marvellous!

[JetsetBkk]

TCP Optimizer will display your current router setings and you can tweak them if you wish.

Hope this helps you.

It certainly did. I've adjusted the MTU setting - 1440 is too big, 1420 is OK, so I set it to 1400.

I've also discovered that a minor irritation with using the Nationwide web site with Firefox (the 'log off' button disappears) is caused by one of my Firefox extensions - running with a clean Firefox profile doesn't have the problem. Internet Explorer is always OK.

Thanks for your help Katoey - much appreciated.

[Khun Jean]

I run a few websites and i think this MTU setting is actually a problem of the bank. If they would change their MTU to 1400 problems like this are 99% solved.

In my case i changed it to 1440 on all my webservers and problems where solved. As someone who is depended that customers can use a website it is very important to solve the problem server side if possible.

There are so many different routers,switched and not only the last one the customer uses but also 'down the road'. It is impossible to know solutions for al those different types and even more difficult to instruct people how they can change their own MTU.

so if this is the case:

I have eventually got an intelligent response from one of the support guys who admits that other customers have had the same problems. His response states that the MTU [Maximum Transmission Unit, TCP/IP] of my ADSL router is too low, meaning that it doesn't send a complete message or packet back to the web site:

It is time he changed the MTU on their servers as it has a good chance to fix the problem too. At least a test case to determine if a change on their side is enough should be made and maybe you can be a good test case.

A call to the bank to suggest this would be very well received i think, as it could probably solve the problems with other users.

Edited January 19, 2008 by Khun Jean

[Prasert]

I don't agree with changing the servers MTU settings.

Each medium has it's own MTU default size. For ethernet it's 1500 (actually 1492), for tokenring it's 4400 and for a serial link it's 576. Routers between these different networks take care of passing these different size packets by informing each other by using icmp (setting the "don't fragment" bit).

More and more networks, especially banks, simply block icmp at their outer firewalls, thinking it's safer. By doing so, they also create problems. So the solution lies not in decreasing mtu sizes at the server's interface, but running the networks in between completely compliant to standards (including end-user routers!).

Blocking icmp is a human error and if one cannot overcome that, changing your servers mtu size is just a patch, not a solution.

Edited January 19, 2008 by Prasert

[JetsetBkk]

It is time he changed the MTU on their servers as it has a good chance to fix the problem too. At least a test case to determine if a change on their side is enough should be made and maybe you can be a good test case.

A call to the bank to suggest this would be very well received i think, as it could probably solve the problems with other users.

That is a very good idea - I'll send the guy a message later.

What really annoys me is that it took me over a month and many messages to the bank (~12) before anyone on their "Help desk" mentioned the MTU setting. They just didn't know about it. And all that time I was searching the web, trying different things until this one guy at the bank comes up with the response I needed.

It's interesting that he twice quoted 1200 to 1420 as the MTU settings to try, and yet, according to other posters, 1452 or 1492 appear to be the common settings for routers. So why is he recommending such a low value? As you say, it may be because that's how their servers are set up, but he is implying that it is the router that cannot send large packets correctly, so it's best to reduce the maximum size sent in order to get the data sent correctly, even if it takes more packets. He doesn't say that his servers can't receive large packets, in fact he implies that they can. I suppose - as somebody once said - "He would say that, wouldn't he."

In my last message to him I did ask him to "publicise this problem and the solution" to the other "Help desk" personnel as I am sure it is going to happen to other people. Hopefully a Google search will turn up this thread for someone looking for a solution to the problem.

So yes, I will tell him that, if he can get it changed, I will happily re-test the site with my MTU set back to 1492. But I get the feeling he won't be too interested. If he isn't, maybe I can find another department at Nationwide that is.

[JetsetBkk]

I don't agree with changing the servers MTU settings.

Each medium has it's own MTU default size. For ethernet it's 1500 (actually 1492), for tokenring it's 4400 and for a serial link it's 576. Routers between these different networks take care of passing these different size packets by informing each other by using icmp (setting the "don't fragment" bit).

More and more networks, especially banks, simply block icmp at their outer firewalls, thinking it's safer. By doing so, they also create problems. So the solution lies not in decreasing mtu sizes at the server's interface, but running the networks in between completely compliant to standards (including end-user routers!).

Blocking icmp is a human error and if one cannot overcome that, changing your servers mtu size is just a patch, not a solution.

Oops, we cross-posted. It's getting a bit too technical for me now! but I think I understand what you're saying. I'll see what the guy has to say about his servers' MTU settings, but he may not be technical enough to answer. "Running networks completely compliant to standards" sounds a good idea - as does producing a browser called "Internet Explorer" completely compl......

Thanks for your input - it's an interesting subject but "does my head in" after a while!

[Katoey]

We've always mistrusted routers supplied by ISP's, no matter what country you live in. ISP's just cannot resist tweaking the routers firmware to be advantageous to the ISP, not the customer.

Hence we always advise clients to purchase their own router and then run the set-up wizard to their particular ISP's specifications. As the client learns more about their own router, they become quite comfortable implementing more advanced tweaks that increase the routers performance while maintaining site security.

Remember to keep your Firewall, Anti-Virus and Spyware/Trojan software up-to-date.

[99BigLad99]

I have just found this topic here and would like to put my two penneth in

Last year I had a similar problem to the OP and doing transfers with NWide (but from about July 07) although internal transfers will work OK. The help desk suggested over a period of six months and countless alterations both MTU and hardware (router) alterations all to no avail. Tried different browsers Firefox IE and Wyzo so many different settings on the MTU I have lost count. A Microsoft trained techie (network & security trained with a high end job) even altered a load of settings on my laptop when in Pattaya still no joy. Yes I have contacted TT&T and pointed this fact out to them they came up with similar suggestions also came and checked the line out at home (with a lot of yakyak from my wife) all to no avail.

HOWEVER

Now i think I have found the problem after trying so many different things and even different computers (wife has an internet shop) on TT&T it is some thing to do with the server TT&T. Just try TOT or IPStar and it all works fine no matter what the MTU is set at. So now all I have to do is take my lap top to some place where they have TOT or IPStar and wonderful I can do all my internet banking without problems.

So if anybody has found a solution that works I would be most interested so would Nationwide and so would TT&T but in the meantime TOT and IPStar seem the way to go.

In Pattaya the Shamrock Bar Pattayaland Soi2 gives a free WiFi connection on TOT and up country anybody with a satellite connection is on IPStar

Oh by the way The Shamrock Bar also has a laptop you can use freebie on the bar if you really want to do internet banking on a public computer (a memory stick is a good thing to work from if you have to use a public computer remember

[JetsetBkk]

So if anybody has found a solution that works I would be most interested so would Nationwide and so would TT&T

Thanks for your post.

What I found was that I could use all the functions of the Nationwide site at an Internet Cafe, but not on my laptop after December last year. So it was then that I started hammering Nationwide with questions and eventually got the MTU response. All was well after I changed the MTU to 1420.

So did you actually change your MTU to 1420 while on TT&T? Bear in mind that my ADSL modem/router does not have an MTU configuration setting, so I used the "TCP Optimizer" from Speedguide.net to change it in my laptop. Have you used "TCP Optimizer" to change your MTU setting?

Edit:

If you have changed your PC's MTU value and it still doesn't work then your problem isn't the same as mine was.

The guy at Nationwide that I talked to was James Cruttenden - he seemed to know his stuff.

Edited April 3, 2008 by JetsetBkk

[99BigLad99]

So if anybody has found a solution that works I would be most interested so would Nationwide and so would TT&T

Thanks for your post.

What I found was that I could use all the functions of the Nationwide site at an Internet Cafe, but not on my laptop after December last year. So it was then that I started hammering Nationwide with questions and eventually got the MTU response. All was well after I changed the MTU to 1420.

So did you actually change your MTU to 1420 while on TT&T? Bear in mind that my ADSL modem/router does not have an MTU configuration setting, so I used the "TCP Optimizer" from Speedguide.net to change it in my laptop. Have you used "TCP Optimizer" to change your MTU setting?

Edit:

If you have changed your PC's MTU value and it still doesn't work then your problem isn't the same as mine was.

The guy at Nationwide that I talked to was James Cruttenden - he seemed to know his stuff.

answers to all is yes and the guy I was in contact with at NW I cant remember his name without going into the account as all was done on the message facility which I could use with smaller messages. As you say the guy at NW did seem to know his stuff but in the end came to the conclusion that my line at home with TT&T was at fault we did many tests and I was sending results to him by taking screen shots and hosting the JPG giving him a link to it. A couple of friends that have stayed with me have also had the same problems with NW from my location so may be as you say it is a different problem to yours.

However having said all that I go into Secrets Hotel and Bar in Pattaya in a morning when in Pattaya to use their free wifi and have breakfast, there upto about three weeks ago I could do internet banking no problem but last time there I could not and the only alteration was that they had disconnected one of the ADSL lines that they had (the one that I used to use called wombat ) and up gradded the other line known as Secrets and guess what - the one that I used to use was TOT and the Secrets one is TT&T, so this reinforces my view that it is the server more than anything.

Edited April 4, 2008 by mgc

[JetsetBkk]

answers to all is yes and the guy I was in contact with at NW I cant remember his name without going into the account as all was done on the message facility which I could use with smaller messages.

Well, that is such a da.mn shame as all your symptoms seem to be the same as mine were, and all were fixed for me with the MTU value change.

As you say the guy at NW did seem to know his stuff but in the end came to the conclusion that my line at home with TT&T was at fault we did many tests and I was sending results to him by taking screen shots and hosting the JPG giving him a link to it. A couple of friends that have stayed with me have also had the same problems with NW from my location so may be as you say it is a different problem to yours.

However having said all that I go into Secrets Hotel and Bar in Pattaya in a morning when in Pattaya to use their free wifi and have breakfast, there upto about three weeks ago I could do internet banking no problem but last time there I could not and the only alteration was that they had disconnected one of the ADSL lines that they had (the one that I used to use called wombat ) and up gradded the other line known as Secrets and guess what - the one that I used to use was TOT and the Secrets one is TT&T, so this reinforces my view that it is the server more than anything.

Yes, that does point the finger at TT&T. I'll just check now that I can do another transfer - maybe something else has changed!

Edit:

Yes, I can still do transfers so I'm afraid I can offer no more ideas. Best of luck and please let us know if you ever resolve the problem as it may well affect others in the future.

Edited April 4, 2008 by JetsetBkk