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Intermittent DNS lockup, any ideas ?

mwwilson
Newbie
Posts: 6
Registered: 18-02-2008

Intermittent DNS lockup, any ideas ?

A fairly recent problem (so 'it used to work' ) applies, also observed with another PN user.
After a few hours, often shortly after a period of no traffic, the following fault will sometimes appear:
I'll be unable to reach any *new* websites or run email if I had not got the programme open already.
I clearly still have some internet access; mail to and from all accounts, access websites I've already been to in the browser I've got open.
Cannot get any access via a new mail or browser session.
To fix this requires a router hard (power) reboot, not just dropping the ADSL line.
Router is D-Link DSL-G604T
All wired, wirelsss off.
ADSL Line is very good: 448/7616 speed, margins 24dB noise 12dB. (Yes, the big building next door says 'BT Exchange' on it  Wink)
Fairly normal WinXP setup, Outlook Express / Firefox / Opera / IE6
I've tried auto DNS, I've tried manual DNS (212.159.6.9 & 212.159.6.10) and I've tried other DNS (Google 8.8.4.4 & 8.8.8.Cool
So, your thoughts on what to try next......
Bill
18 REPLIES
Community Veteran
Posts: 5,472
Thanks: 292
Fixes: 4
Registered: 11-08-2007

Re: Intermittent DNS lockup, any ideas ?

When you said "I've tried manual DNS", was that in the router settings, or in Windows network settings ?
mwwilson
Newbie
Posts: 6
Registered: 18-02-2008

Re: Intermittent DNS lockup, any ideas ?

Router setup
Community Veteran
Posts: 1,101
Registered: 10-09-2010

Re: Intermittent DNS lockup, any ideas ?

What DNS is set on your computers?
Community Veteran
Posts: 5,472
Thanks: 292
Fixes: 4
Registered: 11-08-2007

Re: Intermittent DNS lockup, any ideas ?

So try setting your Windows XP network connection TCP/IP properties to manual DNS as primary 208.67.222.222 (OpenDNS) and secondary to 8.8.8.8 (Google DNS).  If this gives you a reliable service, then it would indicate that there might be an issue with your router's firmware.
You could check the D-Link website to see if there are any firmware updates for your router.
Please report back as to whether bypassing the router's DNS caching server fixes your problem  Smiley
Community Veteran
Posts: 1,101
Registered: 10-09-2010

Re: Intermittent DNS lockup, any ideas ?

For the purposes of testing it's OK, but I would not normally use both OpenDNS and GoogleDNS as for the same query those servers can and often will give different results.
OpenDNS settings are:
208.67.222.222
208.67.220.220
GoogleDNS settings are:
8.8.8.8
8.8.4.4
Community Veteran
Posts: 5,472
Thanks: 292
Fixes: 4
Registered: 11-08-2007

Re: Intermittent DNS lockup, any ideas ?

Which is exactly why I chose those numbers  Roll eyes
I have done a lot of DNS testing (in finding optimum upstream DNSes for my own caching DNS server), and to be fair the results that OpenDNS give differently from Google's, are those sites that Google own - such as YouTube !
I have also observed that for more than 90% of the day that OpenDNS is by far the quickest - compared to Google or PlusNet DNSes.
mwwilson
Newbie
Posts: 6
Registered: 18-02-2008

Re: Intermittent DNS lockup, any ideas ?

to fourfourdevon, PC was set for 'automatic' DNS (ie ask the router) , and I had set up the router with one PN and one google or OpenDNS server.
Now trying the manual setup there as suggested, will give it a week to be significant, I'd usually get a lockup 3 or 4 times a week.
I would add that:
The router had been fine for several years, so I have not applied any updates.
The other setup with the same problem  (my parents, for whom I'm the support department of course !)  is a different router type (Draytek 2500) but also on PN.  I think they are still on default settings.
Thanks for the suggestions so far
Bill

Community Veteran
Posts: 5,472
Thanks: 292
Fixes: 4
Registered: 11-08-2007

Re: Intermittent DNS lockup, any ideas ?

I had a Linksys WAG54Gv3 that showed these symptoms, I was NOT running DHCP as all my PCs are on static IP addresses, but they all used the router for DNS lookups.  This worked fine for several years, but then it became noticeable that the Windows XP PCs started showing DNS lookup lockouts like you are describing, and the only way to clear the problem appeared to be resetting the router.  What was strange though is that I also ran several Ubuntu Linux PCs with static IP addresses and DNS lookup via the router - BUT these machines would NOT show the same DNS lockout, even if the router had apparently stopped responding to the XP machines !.  Since then I built a dedicated Ubuntu caching DNS server for my home network and the problem just disappeared !  Smiley
MJN
Aspiring Pro
Posts: 1,094
Thanks: 45
Fixes: 2
Registered: 26-08-2010

Re: Intermittent DNS lockup, any ideas ?

Quote from: purleigh
I have done a lot of DNS testing (in finding optimum upstream DNSes for my own caching DNS server)

If you're running your own recursive caching DNS server then you ought to cut out any upstream resolvers so as to avoid any delays, problems and quirks that they might have. Stick to root hints instead then you're in complete control (or at least as complete as you ever can be with DNS).
Regarding the OP's problem I agree that it sounds like it is the router acting as an intermediate resolver that is causing problems. I suspect it's another case of the fact that residential routers are made down to a cost and hence the quality of firmware can suffer and whilst in general terms this often does not matter it can do when it comes to critical showstoppers such as DNS failing to operate correctly at all times. As DNS configuration becomes more complex through layering (particularly given the increase of geographic-aware DNS resolution) these nuances will increasingly bring these poor implementations out of the woodwork.
Unless you are willing/able to operate your own recursive DNS resolver then the best solution is probably as the guys have said - hard code your clients with your 3rd party DNS servers of choice... Which to choose is an entirely different debate as there are pros and cons with them all.
Mathew
loungehake
Dabbler
Posts: 24
Registered: 15-07-2008

Re: Intermittent DNS lockup, any ideas ?

I have used OpenDNS for several years and would not willingly use any other name resolution service.  It is blisteringly fast, extremely reliable and offers excellent security enhancements and elective blocking of unwanted web browsing categories.  I enjoy a pleasant freedom from gambling web pages and an almost complete removal of the threat of phishing.
Smiley
Community Veteran
Posts: 5,472
Thanks: 292
Fixes: 4
Registered: 11-08-2007

Re: Intermittent DNS lockup, any ideas ?

[quote=MJN]Stick to root hints instead then you're in complete control
Thanks for that tip, I hadn't heard of 'root hints' before, I will have to read up on the subject and experiment and see if I can get even better DNS response times.  Wink
My existing caching DNS server uses a list of my chosen fastest upstream resolvers from several sources, then when it gets a cache miss it simultaneously does a DNS lookup request from ALL the upstream resolvers in the list and accepts the response which comes back quickest.  This has given me dramatically improved speed and reliability compared with just using the DNS resolver in my ADSL gateway, or using manually setting DNS server addresses on each of my computers.  Grin

[quote=loungehake]I have used OpenDNS for several years and would not willingly use any other name resolution service
I agree, I will always have OpenDNS included in my DNS resolver list because, as you say, it is VERY fast and the filtering is great, especially for my childrens PCs.
Community Veteran
Posts: 1,101
Registered: 10-09-2010

Re: Intermittent DNS lockup, any ideas ?

I use OpenDNS for all those reasons, and I can understand why for basically exactly the same reasons some don't like OpenDNS, but what I can't see the logic of, is using two resolvers, one with all those features and one without, as far as I'm concerned it's just going to be a future source of mysterious problems, to me it like transporting 1 litre of wine and 1 litre of oil in the same bucket, and then even after careful separation wondering why both the oil and the wine are tainted.
Community Veteran
Posts: 1,101
Registered: 10-09-2010

Re: Intermittent DNS lockup, any ideas ?

Quote from: purleigh
I will have to read up on the subject and experiment and see if I can get even better DNS response times.   Wink
It will only slow things down, your resolver will for the most part have to ask for DNS queries to be answered, and using root hints you will have to query the base DNS servers for each domain after following a convoluted chain.
Now OpenDNS have to do the same before answering you, EXCEPT, because their cache is so huge, and they have so many customers, 99% of the time your query is going to be answered from their cache and not by them doing the above.
MJN
Aspiring Pro
Posts: 1,094
Thanks: 45
Fixes: 2
Registered: 26-08-2010

Re: Intermittent DNS lockup, any ideas ?

Quote from: fourfourdevon
Quote from: purleigh
I will have to read up on the subject and experiment and see if I can get even better DNS response times.  Wink
It will only slow things down, your resolver will for the most part have to ask for DNS queries to be answered, and using root hints you will have to query the base DNS servers for each domain after following a convoluted chain.

Absolutely. I should've worded it better - my suggestion was not one for improving response times for when everything is working but rather increasing reliability and freedom of manipulation of results (intentional or otherwise) and the potential for delays if/when the 3rd party resolvers are playing up (ISP resolvers in particular). Besides which, a properly running DNS setup ought not to be introducing any noticable delays into connection setups.
Apologies to the OP for taking this off-topic - this discussion isn't going to help you with your issue so we can continue elsewhere if required.
Mathew