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  Reply # 789114 29-Mar-2013 09:40
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freitasm:
cbrpilot: Your modem looks like it is picking up Telecom's DNS which is great.


How did you get that impression? Looking at What are Telecom's DNS servers page it seems these are the Telecom DNS:

New Primary202.27.158.40shelob.xtra.co.nzNew Secondary202.27.156.72ungoliant.xtra.co.nz
But the OP says:

rhysjenz: Umm, from the router Status page, primary DNS server is 122.56.237.1 and the secondary DNS server is 210.55.111.1 ...?


These addresses are not even close to the Telecom ones. I still think his modem is using wrong DNS.





Actually, the addresses he has shown are valid Telecom DNS addresses for some customers. They aren't addresses anyone should hardcode into their PCs or routers as they aren't reachable by all customers - but if they are assigned automatically, they are the optimal servers to use.

However, for the purposes of troubleshooting, the two 202.27.x.x addresses would be fine to test out.

Short of something like an MTU issue, this doesn't sound like a modem issue. The number of possible failures that would affect only some sites and not others is pretty small (and MTU is a classic example)

I'm out on an Easter Egg hunt now but if the original poster could PM me his IP address and a couple of sites that are still reliably failing, I'll add those sites to my monitoring platform later today and see if I can replicate the issue.

Please include a thorough description of the failure like the error code that comes up in the browser and how long it takes to come up.

Regards
N.



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  Reply # 789218 29-Mar-2013 12:50
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Wow okay so I changed the MTU in the router settings to 1500, and lo and behold, web browsing now works!
I ran a couple speedtests, and am getting ~30ping/~10down/~1up, seems to be working fine.
Thanks for the help guys (especially cbrpilot), you did better than Telecom :)

PS: What was going on there? Telecom actually says to use 1492 so...? TL;DR of what was wrong? Thanks again.

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  Reply # 789225 29-Mar-2013 13:14
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rhysjenz: Wow okay so I changed the MTU in the router settings to 1500, and lo and behold, web browsing now works!
I ran a couple speedtests, and am getting ~30ping/~10down/~1up, seems to be working fine.
Thanks for the help guys (especially cbrpilot), you did better than Telecom :)

PS: What was going on there? Telecom actually says to use 1492 so...? TL;DR of what was wrong? Thanks again.


You're very welcome.  Have to give some credit to l43a2 who first suggested it may be an MTU issue - and your symptoms did very much fit with that sort of issue.

I cannot be sure of what was occurring, but it is very possible that something funky was going on with the PPP LCP negotation where the MTU/MRU is exchanged/agreed between the BNG and modem.  I.e. the modem said one thing, and did another?
Either that or it does not support MSS-clamping.  Probably the later.  

The way this works is that your PC (and other devices) talking out an Ethernet or Wifi interface assume that everything on the other side of the interface supports a full 1500 byte frame.  When the internet link is only set to 1492 rather than 1500, this presents an issue.  Some sites will work as they allow their packets to be fragmented, others don't.  Most modems support MSS-Clamping which is where the modem intercepts the TCP session setup and forces both ends to negotiate a smaller packet size.  It may be that your doesn't?

I'm not sure why the Telecom site recommends 1492.  1492 is the correct size for an older PPPoE implementation.  Chorus doesn't use PPPoE on their customer facing interfaces - they're all PPPoA (with a couple of exceptions).   I'd say the information on that page was produced a very long time ago, and no-one has ever questioned that piece of information (probably, to be honest, because very few people understand it).

I'll have a chat to some people on Tuesday and see if I can get that page updated.

I have been known to work for Telecom, but I'm not here as an official representative or anything.




My views are my own, and may not necessarily represent those of my employer.

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  Reply # 789236 29-Mar-2013 13:31
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freitasm:
cbrpilot: Your modem looks like it is picking up Telecom's DNS which is great.


How did you get that impression? Looking at What are Telecom's DNS servers page it seems these are the Telecom DNS:

New Primary202.27.158.40shelob.xtra.co.nzNew Secondary202.27.156.72ungoliant.xtra.co.nz
But the OP says:

rhysjenz: Umm, from the router Status page, primary DNS server is 122.56.237.1 and the secondary DNS server is 210.55.111.1 ...?


These addresses are not even close to the Telecom ones. I still think his modem is using wrong DNS.





My Telecom DNS servers are listed as 122.56.237.1, 210.55.111.1




Regards,

Old3eyes


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  Reply # 789278 29-Mar-2013 14:47
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Don't you love ISP support pages that don't actually reflect real world when it comes to DNS?




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  Reply # 789339 29-Mar-2013 18:33
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freitasm: Don't you love ISP support pages that don't actually reflect real world when it comes to DNS?


Telecom's page does reflect the real world.  As Talkiet described, not all Telecom customers can access the newer DNS servers, so it makes little sense to put those servers on the Telecom page as it will break some customer's internet if they try and use them.  All BB users will eventually be migrated over to use the newer servers.

All of the DNS servers on the Telecom support pages will work for all Telecom customers.






My views are my own, and may not necessarily represent those of my employer.

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  Reply # 789386 29-Mar-2013 20:03
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cbrpilot:
freitasm: Don't you love ISP support pages that don't actually reflect real world when it comes to DNS?


Telecom's page does reflect the real world.  As Talkiet described, not all Telecom customers can access the newer DNS servers, so it makes little sense to put those servers on the Telecom page as it will break some customer's internet if they try and use them.  All BB users will eventually be migrated over to use the newer servers.

All of the DNS servers on the Telecom support pages will work for all Telecom customers.


The other wrinkle in this is that the OP would have never had this problem if they had been using a Telecom supplied modem. So then it becomes a process of diagnosis of the customers quirks with their own modem.

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  Reply # 793025 4-Apr-2013 11:16
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I'd just like to add that this thread helped us solve the same problem one of our clients was having.

They are a new Telecom business customer, with a new ADSL connection. This week they reported the same symptoms.

We had specifically set the MTU to 1492 (from 1500) as that was detailed in the email the client got from TNZ when their static IP was provisioned.

Today, once we changed it to back to 1500, they could access all the sites that they were having problems with.





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  Reply # 793706 5-Apr-2013 09:46
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The Telecom help page has been changed to show a recommended MTU of 1500.




My views are my own, and may not necessarily represent those of my employer.

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