Question Some issues with making debian work as a dns server

Feb 14, 2020
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Hi everyone,

In order to practice with linux networking, I installed two VMs (debian 10.4) in my VMware workstation. The first one is connected to my home LAN via bridge mode and gets an Ip address (192.198.3.96) from my router directly for its ens33 virtual interface. The second one is connected to the first one through ens37 interface which has 10.10.10.1 as its LAN IP. Basically, the linux first machine works as a DHCP/DNS and firewall for the second one. I also disabled systemd-resolved and installed dnsmasq. Everything worked fine and both virtual machines could browse the internet.

I'd like now to use my debian machine as my real Home LAN dns server too. 192.168.3.0/24 is my physical LAN subnet.

So, I set my debian IP (192.168.3.96) as my main dns server in my LAN router. To test it I temporarily disabled ufw firewall, but I'm still struggling with making it work properly.
It seems that debian doesn't give any response back to my lan devices dns query requests. So I ran tcpdump on the debian machine and ping bbc.co.uk on my pc windows:

Code:
root@debianser:~# tcpdump -i ens33 udp port 53
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ens33, link-type EN10MB (Ethernet), capture size 262144 bytes
11:32:57.422826 IP 192.168.3.100.61615 > 192.168.3.96.domain: 40482+ A? bbc.co.uk. (27)
11:32:57.425602 IP 192.168.3.96.43842 > dns.google.domain: 23581+ PTR? 96.3.168.192.in-addr.arpa. (43)
11:32:57.465074 IP dns.google.domain > 192.168.3.96.43842: 23581 NXDomain 0/0/0 (43)
11:32:57.465449 IP 192.168.3.96.37213 > dns.google.domain: 33433+ PTR? 100.3.168.192.in-addr.arpa. (44)
11:32:57.502468 IP dns.google.domain > 192.168.3.96.37213: 33433 NXDomain 0/0/0 (44)
11:32:57.503148 IP 192.168.3.96.41560 > dns.google.domain: 31282+ PTR? 8.8.8.8.in-addr.arpa. (38)
11:32:57.539584 IP dns.google.domain > 192.168.3.96.41560: 31282 1/0/0 PTR dns.google. (62)
11:32:58.421501 IP 192.168.3.100.61615 > 192.168.3.96.domain: 40482+ A? bbc.co.uk. (27)
11:32:59.427197 IP 192.168.3.100.61615 > 192.168.3.96.domain: 40482+ A? bbc.co.uk. (27)
11:33:01.438172 IP 192.168.3.100.61615 > 192.168.3.96.domain: 40482+ A? bbc.co.uk. (27)
11:33:05.445849 IP 192.168.3.100.61615 > 192.168.3.96.domain: 40482+ A? bbc.co.uk. (27)
11:33:09.448369 IP 192.168.3.100.54401 > 192.168.3.96.domain: 18340+ A? dns.msftncsi.com. (34)
11:33:10.453264 IP 192.168.3.100.54401 > 192.168.3.96.domain: 18340+ A? dns.msftncsi.com. (34)
11:33:11.459111 IP 192.168.3.100.54401 > 192.168.3.96.domain: 18340+ A? dns.msftncsi.com. (34)
Could you please help me figure it out?
Thanks
 

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