[SOLVED] Ubuntu 20.04 unable to resolve by name but 1.1.1.1 and 8.8.8.8 are OK

sundry_50 · 07-25-2021, 04:44 PM

I can ping local machines and 1.1.1.1 and 8.8.8.8 but not google.com or fark.com, etc.

Code:

iptables -nvL
Chain INPUT (policy ACCEPT 1792 packets, 310K bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     tcp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:53 /* managed by anbox-bridge */
    0     0 ACCEPT     udp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            udp dpt:53 /* managed by anbox-bridge */
    0     0 ACCEPT     tcp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:67 /* managed by anbox-bridge */
    0     0 ACCEPT     udp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            udp dpt:67 /* managed by anbox-bridge */

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     all  --  *      anbox0  0.0.0.0/0            0.0.0.0/0            /* managed by anbox-bridge */
    0     0 ACCEPT     all  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            /* managed by anbox-bridge */

Chain OUTPUT (policy ACCEPT 1469 packets, 174K bytes)
 pkts bytes target     prot opt in     out     source               destination

and

Code:

cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 127.0.0.53

Other machines are able to resolve just fine so I don't know what to do next.

TB0ne · 07-25-2021, 05:24 PM

Quote:

Originally Posted by sundry_50

I can ping local machines and 1.1.1.1 and 8.8.8.8 but not google.com or fark.com, etc.

Code:

iptables -nvL
Chain INPUT (policy ACCEPT 1792 packets, 310K bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     tcp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:53 /* managed by anbox-bridge */
    0     0 ACCEPT     udp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            udp dpt:53 /* managed by anbox-bridge */
    0     0 ACCEPT     tcp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            tcp dpt:67 /* managed by anbox-bridge */
    0     0 ACCEPT     udp  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            udp dpt:67 /* managed by anbox-bridge */

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     all  --  *      anbox0  0.0.0.0/0            0.0.0.0/0            /* managed by anbox-bridge */
    0     0 ACCEPT     all  --  anbox0 *       0.0.0.0/0            0.0.0.0/0            /* managed by anbox-bridge */

Chain OUTPUT (policy ACCEPT 1469 packets, 174K bytes)
 pkts bytes target     prot opt in     out     source               destination

and

Code:

cat /etc/resolv.conf 
# Generated by NetworkManager
nameserver 127.0.0.53

Other machines are able to resolve just fine so I don't know what to do next.

Well, what are the other DNS servers for those other machines? Do they ALL point back to that 127.0.0.53 address?? That's something I've never seen before...typically you'll have the address of your ISP's DNS server, or the Google DNS servers (8.8.8.8 and 8.8.4.4). Try putting those into your resolv.conf file, and see what happens. Looks like you don't have a valid DNS server, since you can ping out to the Internet.

sundry_50 · 07-26-2021, 09:49 AM

Thanks for the reply. I'll investigate your suggestion re DNS resolver. The comments in /etc/resolv.conf from the laptop provides a couple of hints. Ubuntu and Mint all reference 127.0.0.53.

Code:

Desktop2 Ubuntu 20.04
#This file is managed by man:systemd-resolved(8). Do not edit.
nameserver 127.0.0.53
options edns0 trust-ad
search lan

Mint 20
#This file is managed by man:systemd-resolved(8). Do not edit.
nameserver 127.0.0.53
options edns0 trust-ad
search lan

Ubuntu 20.04 lappy
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.
nameserver 127.0.0.53

The

Code:

systemd-resolve --status

output is 63 lines so I'll reserve it unless requested.

sundry_50 · 07-26-2021, 12:04 PM

Solved. Protonvpn kill switch set up an interface that I had to remove, then log back in the VPN before shutdown or reboot. Shutdown or reboot before logging into the VPN would cause the interface to reappear and block resolver.

Code:

sudo ip link delete "link_name"

Log in the VPN then you may shutdown or reboot. Otherwise, the link persists.

TB0ne · 07-26-2021, 12:09 PM

Thanks for posting the solution.