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sp0
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DNS problems (SERVFAIL)

We have seen intermittent problems over the last week or so, where VM's DNS server is not finding things it should - stable DNS entries, not new ones that would not yet have propagated.  The effect is Safari saying servers weren't found - and a few mins later if we refresh the window, they appear OK.

Here is an example.  On this occasion, 194.168.8.100 reports SERVFAIL:

dig @194.168.8.100 reportonline.thamesvalley.police.uk

; <<>> DiG 9.8.3-P1 <<>> @194.168.8.100 reportonline.thamesvalley.police.uk
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 61584
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;reportonline.thamesvalley.police.uk. IN A

;; Query time: 14 msec
;; SERVER: 194.168.8.100#53(194.168.8.100)
;; WHEN: Fri Mar 31 13:49:45 2017
;; MSG SIZE rcvd: 53

and for comparison the other VM DNS server reports the correct DNS entry:

dig @194.168.4.100 reportonline.thamesvalley.police.uk

; <<>> DiG 9.8.3-P1 <<>> @194.168.4.100 reportonline.thamesvalley.police.uk
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52809
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;reportonline.thamesvalley.police.uk. IN	A

;; ANSWER SECTION:
reportonline.thamesvalley.police.uk. 300 IN A	195.27.52.210

;; Query time: 15 msec
;; SERVER: 194.168.4.100#53(194.168.4.100)
;; WHEN: Fri Mar 31 13:38:54 2017
;; MSG SIZE  rcvd: 69

While we could of course switch to Google or OpenDNS, we would prefer to use VM's servers but the stability concerns us.  

Perhaps someone from VM could pass this to the technical team.  I don't fancy my chances starting at the call centre with this one!

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TonyMcConnell
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Message 2 of 8
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Re: DNS problems (SERVFAIL)

I am also having this problem. I have tried engaging virgin media via Twitter and they've redirected me to these forums.

I am having to use google's DNS at 8.8.8.8, since Virgin's DNS seems so unreliable.

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Forum Team
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Re: DNS problems (SERVFAIL)

Hello sp0

 

Welcome to our forum, I am sorry you are having intermittent problems resolving on our DNS. I have had a chat with our engineers about it and the SERVFAIL message usually signifies that we didn’t have the record in our cache, sometimes we have problems getting the latest update from the servers from the domain, in the example you gave us the TTL is only 5 minutes and so this may need to happen quite frequently, is there a reason it is that low by the way. 

We were unable to find a problem or reproduce it but will certainly keep an eye on things.

 

Thank you

 

Nicola

Virgin Media Forum Team
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sp0
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Happening again: DNS problems (SERVFAIL)

I have again encountered a situation where a site is listed correctly in all other DNS providers I've tried, but not in VM's DNS or fallback DNS.  Effectively this renders a website (or company) unreachable for all VM customers.

I wonder if something is going wrong with DNS replication on VM's servers?

In this case it's dpd.co.uk (one of the UK's main courier firms) and on VM I get this (in response to "dig dpd.co.uk" on a Mac console) after a 5 second delay:

 

dig @194.168.4.100 dpd.co.uk

; <<>> DiG 9.8.3-P1 <<>> @194.168.4.100 dpd.co.uk
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 49858
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;dpd.co.uk.			IN	A

;; Query time: 5 msec
;; SERVER: 194.168.4.100#53(194.168.4.100)
;; WHEN: Tue Jun 20 08:18:44 2017
;; MSG SIZE  rcvd: 27

and the same on the VM fallback DNS 194.168.8.100.

whereas on (eg) Google's DNS, OpenDNS, or the DNS on my various cloud-hosted Unix boxes I get this instantly:

dpd.co.uk. 3176 IN A 89.207.48.222

Perhaps the site owner has messed up something in their DNS entry but I would have thought that mess would be equally reflected around the net not just on VM?

Sometimes DNS issues clear eventually by themselves.  I've given this about 11 hours so far.

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AlphaTangoKilo
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Message 5 of 8
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Re: Happening again: DNS problems (SERVFAIL)

Been having the exact same problem today. unable to connect to dpd.co.uk  to track a parcel I was expecting.

if I add the ip address  

89.207.48.222 into the address bar it connects first time 

if I use google dns 8.8.8.8 it works first time

Sp0's dns server looks like its number 53 haven't a clue what mine is I don't have dig installed on this machine

talking to second line is like the most frustrating exercise ever as nobody seems to know what a dns server does. suggestions such as dpd are blocking you are meaningless as it translates the ip address just not the long domain name. Just because it works for them doesn't mean it works on every dns server on the network.

It is a Virgin issue that has nothing to do with my 3rd party equipment as I can connect via every other dns service.

DPD have not blocked any virgin media customers

I suggest there is a corrupt line in #53 dns server and possible others too

First noticed this around 1200 today now 2200 and still there

 

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sp0
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Message 6 of 8
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Re: Happening again: DNS problems (SERVFAIL)

FYI: 53 is not the number of a DNS server, it's a port number - all calls to DNS use this port.  And if you are on Windows you can use NSLOOKUP to check what is being retrieved from your DNS servers.

That particular site seems now to be in Virgin Media's DNS again (24 hours later).  However I do think there are intermittent problems with updates not finding their way into VM's DNSes, when other major DNSes receive the updates satisfactorily.  

Above all I wonder whether VM's DNSes are monitored with the close attention that is so critical for all of VM's customers.  And whether there is am appropriately speedy route for problem reporting and escalation.

When a business disappears from the DNS, locking out all of VM's customers nationwide, that can have a significant economic impact for the business and/or VM's customers.

 

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AlphaTangoKilo
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Message 7 of 8
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Re: Happening again: DNS problems (SERVFAIL)

still down almost 3am here now 

89.207.48.222 still working

DPD driver also stated other customer had said no web access this morning too no idea what isp tho 

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AlphaTangoKilo
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Message 8 of 8
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Re: Happening again: DNS problems (SERVFAIL)

back up now first chance to check it since last night could have been up a while

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