cannot access github.com

Question

I cannot nslookup github:

nslookup github 8.8.8.8
;; connection timed out; no servers could be reached

nslookup github.com
;; connection timed out; no servers could be reached

nb: default ns server = gw = router 4g = 192.168.0.1 (a cache dns server I guess). I am on a 192.168.0.0/24, my ip = 192.168.0.130, bcast = 192.168.0.255, ip given by router via dhcp.

my nslookup seems to be working:

nslookup google.com 
Server:     8.8.8.8
Address:    8.8.8.8#53
Non-authoritative answer:
Name:   google.com
Address: 142.250.187.206
Name:   google.com
Address: 2a00:1450:4009:81f::200e

I can tlslookup github.com

tlslookup github.com 
140.82.113.4

nb: I dont know why resolution works with this tool and not with nslookup. I tried to grab infos regarding tlslookup over google but nothing.

I check with dig (just in case my nslookup does not work fine). Unfortunately the pb remains with this tool.

dig github.com
; <<>> DiG 9.16.27-Debian <<>> github.com
;; global options: +cmd
;; connection timed out; no servers could be reached

dig @8.8.8.8 github.com
; <<>> DiG 9.16.27-Debian <<>> @8.8.8.8 github.com
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached

Obviously all commands relying on name resolution wont work, but for the sake of the post, I tried some of them:

ping $(tlslookup github.com)
PING 140.82.114.3 (140.82.114.3) 56(84) bytes of data.
64 bytes from 140.82.114.3: icmp_seq=1 ttl=50 time=259 ms
64 bytes from 140.82.114.3: icmp_seq=2 ttl=50 time=317 ms
64 bytes from 140.82.114.3: icmp_seq=3 ttl=50 time=238 ms
^C
--- 140.82.114.3 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 237.514/271.189/316.968/33.546 ms

but

ping github.com
ping: github.com: Temporary failure in name resolution
openssl s_client -connect github.com:443
140311527400768:error:2008F002:BIO routines:BIO_lookup_ex:system lib:../crypto/bio/b_addr.c:730:Temporary failure in name resolution
connect:errno=11

wget github.com 
--2022-04-28 09:52:02--  http://github.com/
Resolving github.com (github.com)... failed: Temporary failure in name resolution.
wget: unable to resolve host address ‘github.com’

I tried to wget website ip address:

wget 140.82.113.3
--2022-04-28 10:01:13--  http://140.82.113.3/
Connecting to 140.82.113.3:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: https://140.82.113.3/ [following]
--2022-04-28 10:01:13--  https://140.82.113.3/
Connecting to 140.82.113.3:443... connected.
The certificate's owner does not match hostname ‘140.82.113.3’

if I browse the ip address, I have got a warning message saying the cert is wrong, if I try to pass it over (accept risk), there is no way to access website.

nothing blocking in my hosts file:

cat /etc/hosts
127.0.0.1   localhost
127.0.1.1   zavata.circus.net   zavata
# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Everything look fine in my routing table (192.168.0.1 beeing my default gw, a 4g router)

route -n 

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    600    0        0 wlp1s0
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 wlp1s0
192.168.0.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp1s0

Many thanx folks !!

Answer 1

It looks like the problem comes from the operator. As soon as I change of FAI/operator, I can access github.com without any issue. I just made an entry in my hosts file to access the website when connected to the faulty FAI.