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Standard User John_Gray
(member) Wed 14-Dec-16 18:25:14
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How to overcome BT's forced DNS servers


[link to this post]
 
We had a new BT Business Broadband ADSL line installed at work today with a static IP address, and are using a Draytek Vigor 2860 router.

Before the ADSL line is established (after a router reboot, say), in
Online Status -> Physical Connection -> LAN Status -> Router Primary DNS and Router Secondary DNS
shows correctly the DNS router addresses I had assigned, namely the Google DNS servers 8.8.8.8 and 8.8.4.4

As soon as the ADSL line connection is established, some 10-20 second later, these addresses are changed to what I presume are BT DNS servers (the IP addresses vary after each reboot).

Has anyone met this? And do you know how to prevent BT's 'forced' DNS routers overriding the ones we specify, for the Draytek 2860 specifically?

TIA!
Standard User PaulKirby
(fountain of knowledge) Wed 14-Dec-16 19:05:20
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Re: How to overcome BT's forced DNS servers


[re: John_Gray] [link to this post]
 
I set my own DHCP Server up which gives out Internal IP Addresses to all connecting devices, it also gives out DNS Addresses too.

Not too sure what OS you are using, but on windows you can also change the DNS Server(s) in the network setting.

Paul

BTBroadband - Infinity 4 - 310Mbps (down), 31Mbps (up)
TBB Speedtest
Standard User TheEulerID
(experienced) Wed 14-Dec-16 20:08:12
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Re: How to overcome BT's forced DNS servers


[re: John_Gray] [link to this post]
 
There is no way that BT can "force" a router to use its DNS addresses (or at least, not third party routers). It's all down to the router's firmware what it does. According to the user manual the Draytek 2860 will default to getting the DNS address from the ISP. However, there appears to be an option to override that. It's covered in page 146 onwards:-

http://www.draytek.co.uk/download/support/userguides...


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Standard User John_Gray
(member) Wed 14-Dec-16 20:33:15
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Re: How to overcome BT's forced DNS servers


[re: TheEulerID] [link to this post]
 
Thank you! That looks very promising.

Do you refer specifically to the option at the bottom of page 148:

Force router to use “DNS server IP address …..”

Force Vigor router to use DNS servers configured in LAN1/LAN2/LAN3/LAN4/LAN5/LAN6 instead of DNS servers given by the Internet Access server (PPPoE, PPTP, L2TP or DHCP server).
Standard User BatBoy
(sensei) Thu 15-Dec-16 09:36:01
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Re: How to overcome BT's forced DNS servers


[re: TheEulerID] [link to this post]
 
Unless BT hijacks port 53
Standard User TheEulerID
(experienced) Thu 15-Dec-16 09:54:21
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Re: How to overcome BT's forced DNS servers


[re: John_Gray] [link to this post]
 
Yes
Standard User TheEulerID
(experienced) Thu 15-Dec-16 09:55:52
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Re: How to overcome BT's forced DNS servers


[re: BatBoy] [link to this post]
 
What I said was "There is no way that BT can "force" a router to use its DNS addresses".

Hijacking port 53 isn't forcing the router to do it. The subject was specifically about router configurations.
Standard User BatBoy
(sensei) Thu 15-Dec-16 10:01:08
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Re: How to overcome BT's forced DNS servers


[re: TheEulerID] [link to this post]
 
The effect is the same though, isn't it?
Standard User 23Prince
(experienced) Thu 15-Dec-16 11:28:39
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Re: How to overcome BT's forced DNS servers


[re: John_Gray] [link to this post]
 
I've always used Google for DNS and it's never been switched but I have also only done it on my actual machines and never at the router.

The HH6 has the option for Custom DNS so I hope that BT have moved away from it - for now I just use Google's IPv6 DNS instead, but again on all my machines only.
Standard User troublegum
(regular) Thu 15-Dec-16 17:34:12
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Re: How to overcome BT's forced DNS servers


[re: BatBoy] [link to this post]
 
In reply to a post by BatBoy:
Unless BT hijacks port 53

They don't.

Edited by troublegum (Thu 15-Dec-16 17:34:30)

Standard User PaulKirby
(fountain of knowledge) Thu 15-Dec-16 18:15:31
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Re: How to overcome BT's forced DNS servers


[re: 23Prince] [link to this post]
 
In reply to a post by 23Prince:
I've always used Google for DNS and it's never been switched but I have also only done it on my actual machines and never at the router.

The HH6 has the option for Custom DNS so I hope that BT have moved away from it - for now I just use Google's IPv6 DNS instead, but again on all my machines only.

And where is this setting, my Smart Hub (i.e. HH6) doesn't have any section that allows you to change the Primary and Secondary DNS Addresses.

Unless I am missing a section.

Paul

BTBroadband - Infinity 4 - 310Mbps (down), 31Mbps (up)
TBB Speedtest
Standard User MCM
(knowledge is power) Thu 15-Dec-16 18:23:59
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Re: How to overcome BT's forced DNS servers


[re: PaulKirby] [link to this post]
 
Including no way to add an ipv6 DNS server where none is currently provided by BT,
Standard User PaulKirby
(fountain of knowledge) Thu 15-Dec-16 18:57:29
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Re: How to overcome BT's forced DNS servers


[re: MCM] [link to this post]
 
In reply to a post by MCM:
Including no way to add an ipv6 DNS server where none is currently provided by BT,

Yeah I noticed that as well when I was setting everything up ready, I was hoping that firmware SG4B1000223E would of added that feature, sadly it didn't

I know I have been looking into setting up an IPv6 DHCP Service to use googles 2 IPv6 DNS Servers, which is to run along side with our IPv4 DHCP Service.

I just haven't got around to doing it yet due to there is no rush to do so yet.

Paul

BTBroadband - Infinity 4 - 310Mbps (down), 31Mbps (up)
TBB Speedtest
Standard User 23Prince
(experienced) Thu 15-Dec-16 20:01:56
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Re: How to overcome BT's forced DNS servers


[re: PaulKirby] [link to this post]
 
I was referring to the Dynamic DNS section?

https://postimg.org/image/4im8dmiwj/

I change my DNS on my device on on my PC and MAC - I didn't say I changed it on the hub. I get 10/10 on the tests so I assume it works.
Standard User PaulKirby
(fountain of knowledge) Thu 15-Dec-16 20:45:21
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Re: How to overcome BT's forced DNS servers


[re: 23Prince] [link to this post]
 
In reply to a post by 23Prince:
I was referring to the Dynamic DNS section?

https://postimg.org/image/4im8dmiwj/

I change my DNS on my device on on my PC and MAC - I didn't say I changed it on the hub. I get 10/10 on the tests so I assume it works.

Oh it was where you mentioned "Custom DNS" I was like no you cannot change the DNS stuff on it LOL.

But yeah I setup my own DHCP Server that also sets the DNS Servers I want to use and tells all our connected devices to use them.

I still need to setup another DHCP Service for IPv6 stuff and then I will be done smile

Paul

BTBroadband - Infinity 4 - 310Mbps (down), 31Mbps (up)
TBB Speedtest
Standard User John_Gray
(member) Fri 16-Dec-16 21:01:34
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Re: How to overcome BT's forced DNS servers


[re: John_Gray] [link to this post]
 
@TheEulerID

Your suggestion was spot on - ticking the box in front of (the abbreviated version of):
Force Vigor router to use DNS servers configured in LAN1/LAN2/LAN3/LAN4/LAN5/LAN6 instead of DNS servers given by the Internet Access server (PPPoE, PPTP, L2TP or DHCP server).
caused the correct DNS server addresses to appear in
Online Status -> Physical Connection -> LAN Status -> Router Primary DNS and Router Secondary DNS

However, I have no idea what function these ISP DNS servers actually have, because, regardless of their content, the router's DHCP hands out the required DNS server addresses to the PCs and laptops on the LAN!
Standard User Oliver341
(eat-sleep-adslguide) Fri 16-Dec-16 21:10:26
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Re: How to overcome BT's forced DNS servers


[re: John_Gray] [link to this post]
 
In reply to a post by John_Gray:
However, I have no idea what function these ISP DNS servers actually have, because, regardless of their content, the router's DHCP hands out the required DNS server addresses to the PCs and laptops on the LAN!

It will be used by the router for its DNS lookups, e.g. looking up NTP server hostnames.

Oliver.
Standard User John_Gray
(member) Sat 17-Dec-16 15:28:42
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Re: How to overcome BT's forced DNS servers


[re: Oliver341] [link to this post]
 
Thanks! It will therefore be looking up uk.pool.ntp.org...
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