Recently both of our DNS servers stopped responding to incoming UDP on port 53, tested with dig and it works with TCP. They both have common ISP. Is there any way to traverse route and find out exactly where the incoming traffic on said port with protocol is being dropped/blocked? NMAP scan shows port as filtered. We have a pfSense firewall and I can see that it works fine with another ISP. It also works if I redirect another port (54) to the DNS server via pfSense.
DNS server is working and queries work from inside the network. To be sure I stopped DNS and used iperf on port 53 with UDP and surely can't connect from outside, iperf with TCP on port 53 and connection gets established.
Tracepath output, not sure why it doesn't stop at finding our ip but contiues.
tracepath -p53 __our_domain__
1?: [LOCALHOST] pmtu 1500
1: 10.0.2.2 0.542ms
1: 10.0.2.2 0.254ms
2: 192.168.0.1 2.652ms asymm 64
3: 10.234.0.1 3.092ms asymm 63
4: broadband.actcorp.in 6.964ms asymm 62
5: 14.141.145.5.static-Bangalore.vsnl.net.in 4.456ms asymm 61
6: no reply
7: 115.110.161.30.static.vsnl.net.in 36.027ms asymm 59
8: no reply
9: no reply
10: 218.248.160.105 22.052ms asymm 56
11: no reply
12: __our_domain__ 57.694ms asymm 54
13: no reply
14: no reply
15: no reply
16: no reply
17: no reply
18: no reply
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21: no reply
