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DNS Problems?

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Rising Star
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DNS Problems?

I have recently been getting those DNS dropouts again on my Win 8 machine, with a long pause until restoration of service. Meanwhile ADSL and TG582n router seem to keep going.

Feels like that old TG582 'WANDOWN' spoofing again, which I fixed in the router so it doesn't lead to Windows cache getting permanently mucked up and needing a restart. But it does cause a break in proceedings. I wonder if ipconfig /flushdns can speed things up?

Has there been a problem with the Plusnet DNS servers?

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Superuser
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Re: DNS Problems?

Ah this old nugget - I recall it well - from four and a half years ago https://community.plus.net/t5/ADSL-Broadband/198-18-1-x-address-problems/m-p/1171169

ipconfig /flushdns

… will cause all DNS resolutions to be erased and require all names to be re-resolved.

However your last post in the above topic identifies an essential additional step to clear the spoofed IP addresses in the router - see https://community.plus.net/t5/ADSL-Broadband/198-18-1-x-address-problems/m-p/1545074#M324019

 

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Rising Star
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Re: DNS Problems?

Hah! Thanks for reminding me of the details of my previous post on this matter. I had a look in the router and this time the address spoofing list was empty. So I just hope this problem will not persist. Possibly should look at replacing the default Plusnet DNS servers in the router.
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Plusnet Help Team
Plusnet Help Team
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Re: DNS Problems?

Hi there, 


Yes, it would be worth trying an alternate DNS (perhaps Google's) to see if the same issue happens. 

If this post resolved your issue please click the 'This fixed my problem' button
 Adam Walker
 Plusnet Help Team
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Superuser
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Re: DNS Problems?

Adam,

Using a different DNS is more than like to avoid the problem rather than fix it. The question never answered back then was why does the router decide to spoof addresses? One has to surmise because a DNS look up failed?
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Community Veteran
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Re: DNS Problems?

Not this again! That question was answered, it's a solved problem, you just didn't like the answer and would prefer to blame something else or claim it's too complicated and we'll never know. I can't see the point of continuing to use fundamentally wrong reasoning to draw the wrong conclusion.

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Superuser
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Re: DNS Problems?

For this user this issue appears to have arisen again and therefore the issue merits review.

Elsewhere we see internal DNS lookup failures causes email not to be delivered / accepted. Changing DNS servers to be not Plusnet appears to ‘solve’ the spoofing problem.

Is my understanding that, these routers spoof IP addresses subsequent to a failed DNS query, flawed? If yes, can you please enlighten us all? If it is not flawed, then asking about the behaviour of the DNS serve seems like a logical question, the answer to which might resolve other odd ball issues.

This is not a matter of not liking the answer then or now. There was no answer regarding what caused the router to start spoofing addresses. The resolutions reached at that time either avoided the scenario (change DNS) or put a plaster on the symptoms (switch off spoofing). In the meantime other DNS intermittent failures impact email functionality - this therefore seems like a reasonable question.
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Re: DNS Problems?


@Townman wrote:
Is my understanding that, these routers spoof IP addresses subsequent to a failed DNS query, flawed?

Yes.

If yes, can you please enlighten us all?

Evidently I can't, considering that I have repeatedly tried and failed before. Perhaps you could re-read that "198.18.1.x address problems" thread. You seem to want to keep asking why a bugged piece of software works most of the time but sometimes goes wrong.

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Superuser
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Re: DNS Problems?

If changing DNS servers removes events which give rise to the spoofing behaviour ,then surely one has to question the dependability of the DNS servers? Elsewhere we see transient DNS failures give rise to domain look ups being returned as does not exist.

As I understand it, such an event would lead to the router appropriately spoofing the address? Thereby the router is doing what it should do rather than being buggy.

What bothers me more both then and now is that there are residual indications that all is not well with the DNS service; such could have ramifications far wider than this issue with an old router. Whilst the solution to this issue is thought to be found in using another DNS address, the elephant is still in the room and no attempt is being made to eat it.
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Rising Star
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Re: DNS Problems?

[For obvious reasons I have censored this post from my original version]

 

Bit of a swerve...

This is just the craziest thing.

While pondering on this matter I logged on to my Technicolor TG582n router and idly started browsing the Help pages. This led me to Google <something>.

I found this address:

<censored>

<censored text> OK, I backed up to:

<this address>

And.... I appear to be logged IN as the admin for a Technicolor router. But IT ISN'T MINE! It's a TG670 v2. Where is it? Whose is it? How come I appear to be logged in as admin to somebody elses router? WHAT?!

Is this an actual physical router or a router simulation web page?

 

IF real I appear to have accidentally just found a method of breaking into unsecured routers...

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Re: DNS Problems?


@Townman wrote:
As I understand it, such an event would lead to the router appropriately spoofing the address?

No. That would not be an intended use of the "WAN Down DNS Spoofing" function. The clue is in its name, specifically the "WAN Down" part. I give up and will do my best to not even read any more of this thread.

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Rising Star
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Re: DNS Problems?

Why would a router, apparently in Israel, have the admin account open and both the firewall and intrusion detection disabled? This appears an open door. Why?

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Aspiring Hero
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Re: DNS Problems?

@pvmb do you have any powerlines in your network?

I've seen reports of people logging into a neighbour's network via unsecured powerlines.

 

Ex-Plusnetter now living life in the G,fast lane!
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Superuser
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Re: DNS Problems?

@ejs

Ah thank you - penny dropped - you are suggesting that spoofing should only occur when there’s a DNS lookup failure AND there is no PPP session?

Such gives clarity to this being a router firmware issue in the circumstances of DNS lookup failures: the correct recovery is not being performed ... to events which ought not to happen. Switching to a more reliable DNS server keeps the router away from its bad code.
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Rising Star
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Re: DNS Problems?


@Browni wrote:

@pvmb do you have any powerlines in your network?

I've seen reports of people logging into a neighbour's network via unsecured powerlines.

 


Nope. Router apparently in a company in Israel. It appears to have a couple of unspecified devices connected on two ethernet ports. A WiFi port and a dual telephone port. Operating about 10 kbps DSL connection.

From the logs, every three seconds there is an attempted login by 'admin'.