[SOLVED]Can't resolve certain domain names

loqs · 2019-01-07 23:31:05

jacopastorius · 2019-01-07 23:37:56

Thank you loqs, I'll create that config file. Do you think network manager service is reading DNS from the ISP modem ?

Last edited by jacopastorius (2019-01-07 23:38:31)

loqs · 2019-01-07 23:46:37

I would suggest checking the journal for records from NetworkManager.
I do not use NetworkManager so I do not know what is recorded by default or what additional information can be obtained by increasing the loglevel.

seth · 2019-01-08 09:37:57

The resolver is typically configured by asking the dhcp server.

sudo nmap --script broadcast-dhcp-discover

Let's assume that's your consumer router at 192.168.1.1 (which is typical)
In this case your consumer router runs a broken DNS server.
You can probably log into that router via a web interface ( http://192.168.1.1/ ) and configure the DNS settings to either:
a) fix its DNS server (maybe by altering the backend IP, DNS servers have an open port 53)
or
b) define a different DNS server (8.8.8.8, 1.1.1.1)

The "normal" behavior for consumer routers is to forward a DNS server run by your ISP via dnsmasq (rather than eg. running https://www.archlinux.org/packages/extra/x86_64/bind/)
Whoever you use as your DNS provider can technically see that you want to know the IP for totallynoporn.xxx, 8888 is google, 1111 is cloudflare and as mentioned, your routers DNS server will likely just ask your ISP. If you're not happy with any of this solutions, you can run a local unbound (or even bind) server on your desktop system (and no: nobody cares that you're a perv. All hu-men are ;-)

jacopastorius · 2019-01-08 15:05:14

Unfortunately i can't set DNS in my ISP router. I just can choose from a predefinite list of DNS server called DynDNS.
I think i'll dig into unbound.
Is it not enough to avoid network manager to overwrite resolv.conf and set my preferred DNS in that file?

seth · 2019-01-08 15:08:04

DynDNS is sth. entirely different (that's to allow your router/network to be accessible from the outside under a domain like me.dyndns.org or whatever)

Is it not enough to avoid network manager to overwrite resolv.conf and set my preferred DNS in that file?

That's entirely sufficient, I just tried to explain on your follow-up questions.

What's the exact modem/router/switch brand/s?

jacopastorius · 2019-01-08 15:14:51

Ok, thank you seth.
The modem/router which accept connection is

Name of device	
AGCOMBO
DSL version	
A2pv6F039u.d26a
Serial Number	
%R045771320N091713BCD9
Firmware version	
AGSOT_1.0.9
Bootloader Version	
1.04.0
Hardware Type & Version	
V01

The modem/router i use just as a router is ASUS DSL-AC52U

seth · 2019-01-08 15:35:23

http://setuprouter.com/router/asus/rt-ac56u/dns.htm ?
The cascade is probably also the problem here, the modem will likely receive a usable DNS server from your ISP, but your router doesn't use it.
Unfortunately the AGCOMBO device seems to be some barebone where ISPs just slap there custom firmware on, does it run a DNS server as well?

nmap -p 53 <ip.of.your.modem>

jacopastorius · 2019-01-08 16:00:43

If I am getting it right, you're saying that if i change DNS to the router which just spread the wifi signal (the Asus), the DNS sended by ISP to my modem/router which receive directly the connection (AGCOMBO) will be ignored and ones set on Asus will be used?

[du@du ~]$ nmap -p 53 192.168.1.1
Starting Nmap 7.70 ( https://nmap.org ) at 2019-01-08 17:00 CET
Nmap scan report for 192.168.1.1
Host is up (0.0013s latency).

PORT   STATE SERVICE
53/tcp open  domain

Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds

Last edited by jacopastorius (2019-01-08 16:03:12)

seth · 2019-01-08 16:03:38

That depends on the actual layout. For a start:
- is 192.168.1.1 the asus router or the AGCOMBO modem?
- What's the IP of the other device? Does it run a DNS server as well?
- Do both run a dhcp server in the same subnet ("sudo nmap --script broadcast-dhcp-discover")

Trilby · 2019-01-08 16:03:58

jacopastorius wrote:

If I am getting it right, you're saying that if i change DNS to the router which just spread the wifi signal (the Asus), the DNS sended by ISP to my modem/router which receive directly the connection (AGCOMBO) will be ignored and the one set on Asus will be used?

The one set on the Asus router is almost certainly just relaying requests to the ISP, so if instead of asking your ISP for an address, you ask your router, and the router asks the ISP and relays the answer back to you. So that would not help at all. Use a *different* external DNS like 8.8.8.8 or 1.1.1.1 suggested above.

jacopastorius · 2019-01-08 16:51:19

Thank you very much guys. So:

192.168.1.1 is the ip of AGCOMBO modem
192.168.1.2 is the ip of the router Asus

[du@du ~]$ sudo nmap --script broadcast-dhcp-discover
[sudo] password for du: 
Starting Nmap 7.70 ( https://nmap.org ) at 2019-01-08 17:48 CET
NSOCK ERROR [0.3420s] nsock_pcap_try_open(): pcap_open_live(enp5s0f1, 1500, 0, 200) failed with error: enp5s0f1: SIOCETHTOOL(ETHTOOL_GET_TS_INFO) ioctl failed: No such device
NSOCK ERROR [0.3420s] nsock_pcap_open(): Will wait 4 seconds then retry.
NSOCK ERROR [0.3420s] nsock_pcap_try_open(): pcap_open_live(enp5s0f1, 1500, 0, 200) failed with error: enp5s0f1: SIOCETHTOOL(ETHTOOL_GET_TS_INFO) ioctl failed: No such device
NSOCK ERROR [0.3420s] nsock_pcap_open(): Will wait 8 seconds then retry.
NSOCK ERROR [0.3420s] nsock_pcap_try_open(): pcap_open_live(enp5s0f1, 1500, 0, 200) failed with error: enp5s0f1: SIOCETHTOOL(ETHTOOL_GET_TS_INFO) ioctl failed: No such device
NSOCK ERROR [0.3420s] nsock_pcap_open(): Will wait 12 seconds then retry.

I tried with their specific ip with the command you suggested few posts ago:

[du@du ~]$ nmap -p 53 192.168.1.1
Starting Nmap 7.70 ( https://nmap.org ) at 2019-01-08 17:49 CET
Nmap scan report for 192.168.1.1
Host is up (0.0012s latency).

PORT   STATE SERVICE
53/tcp open  domain

Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds
[du@du ~]$ nmap -p 53 192.168.1.2
Starting Nmap 7.70 ( https://nmap.org ) at 2019-01-08 17:49 CET
Nmap scan report for 192.168.1.2
Host is up (0.0011s latency).

PORT   STATE  SERVICE
53/tcp closed domain

Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds

seth · 2019-01-08 17:06:33

Ok, so only the AGCOMBO modem provides a DNS server, if you cannot configure the dns provider in the modem (somewhere in the lan/dhcp settings) you're out of luck.
The next thing is the nmap error - this is from an ethernet device, but you suggest some wifi, so let's see how you're actually connected:

ip a
ip r

jacopastorius · 2019-01-08 17:10:21

Unfortunately I can't set DNS in AGCOMBO web interface settings.
May be the ethernet error is somehow reffered to the connection between Asus and AGCOMBO which is by ethernet ports?

Here are the outputs:

[du@du ~]$ ip a                  
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp5s0f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether 78:24:af:c8:b4:3d brd ff:ff:ff:ff:ff:ff
3: wlp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 40:e2:30:cc:01:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.6/24 brd 192.168.1.255 scope global dynamic noprefixroute wlp4s0
       valid_lft 15526sec preferred_lft 15526sec
    inet6 fe80::9b58:976:bb0d:7831/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

[du@du ~]$ ip r
default via 192.168.1.1 dev wlp4s0 proto dhcp metric 600 
192.168.1.0/24 dev wlp4s0 proto kernel scope link src 192.168.1.6 metric 600

Last edited by jacopastorius (2019-01-08 17:13:49)

Trilby · 2019-01-08 17:11:46

seth wrote:

if you cannot configure the dns provider in the modem (somewhere in the lan/dhcp settings) you're out of luck.

What do you mean by this? He can configure the DNS on his own machine to use google or cloudfare, or another.

EDIT: thanks for the clarification below - I likely missed some transitions from just skimming recent activity in the thread.

Last edited by Trilby (2019-01-08 18:56:19)

seth · 2019-01-08 18:44:27

@Trilby, of course - this is just about fixing the router/modem at this point (the thing is handing out a bogus DNS server, so rather than working around that on every possible wifi client, ideally one could make it stop doing that)

@jacopastorius, no this is on your system but that's ok because the ethernet isn't linked at all. I frankly have no idea why nmap doesn't use the wifi interface, looks all ok.
Can you try to wire the ethernet interface to the asus router and run "sudo nmap --script broadcast-dhcp-discover" again? (We want to figure what's providing dhcp, eg. if the asus router does dhcp and happily hands out the modems DNS server but the modem doesn't actually provide that in the current setup, maybe because the router has a static connection to the modem)

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#26 2019-01-07 23:31:05

Re: [SOLVED]Can't resolve certain domain names

#27 2019-01-07 23:37:56

Re: [SOLVED]Can't resolve certain domain names

#28 2019-01-07 23:46:37

Re: [SOLVED]Can't resolve certain domain names

#29 2019-01-08 09:37:57

Re: [SOLVED]Can't resolve certain domain names

#30 2019-01-08 15:05:14

Re: [SOLVED]Can't resolve certain domain names

#31 2019-01-08 15:08:04

Re: [SOLVED]Can't resolve certain domain names

#32 2019-01-08 15:14:51

Re: [SOLVED]Can't resolve certain domain names

#33 2019-01-08 15:35:23

Re: [SOLVED]Can't resolve certain domain names

#34 2019-01-08 16:00:43

Re: [SOLVED]Can't resolve certain domain names

#35 2019-01-08 16:03:38

Re: [SOLVED]Can't resolve certain domain names

#36 2019-01-08 16:03:58

Re: [SOLVED]Can't resolve certain domain names

#37 2019-01-08 16:51:19

Re: [SOLVED]Can't resolve certain domain names

#38 2019-01-08 17:06:33

Re: [SOLVED]Can't resolve certain domain names

#39 2019-01-08 17:10:21

Re: [SOLVED]Can't resolve certain domain names

#40 2019-01-08 17:11:46

Re: [SOLVED]Can't resolve certain domain names

#41 2019-01-08 18:44:27

Re: [SOLVED]Can't resolve certain domain names

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