Networking on Linux

Find all devices in the local network
```
nmap -sn 192.168.1.*
```
List open ports and processes that owns them
```
lsof -i
```
or
```
netstat -tulpn
```
```
ss -tulpn
```
Get process which is bound to port 22
```
lsof -i :22
```
Show both listening and non-listening sockets
```
netstat -a
```
Show all TCP connections
```
netstat -t
```
Display all connections and don’t resolve names
```
netstat -an
```
View processes which are using the network connection
```
netstat -p
```
Get listening ports
```
netstat -napt | grep -i LISTEN
```
Ask the DNS server where the domain can be found - ommit the cache
```
dig www.google.com @ns1.syseleven.de
```
View the packets which go through port 18026 on localhost
```
tcpdump -s 0 -X port 18026 -i lo
```
-s - show the whole package -X - print package data -i lo - use the lo interface, ifconfig will show you the lo interface

View available interfaces with sudo tcpdump -D
Sniff on 10.0.50.2:9200
```
tcpdump -s 0 -X port 9200 and host 10.0.50.2 -i et0
```
Check for the et0 interface with ifconfig
Sniff and save to a file which later can be used with Wireshark
```
tcpdump -s 0 -w file-name.pcap -X port 9000 -i venet0
```
Find the file in: /var/lib/tcpdump/

Quick Wireshark Tips:
- set filter to: http
- right click on a packet > Decode As > Choose the Transport tab and select HTTP

Dig

View only the answer section
```
dig redhat.com +noall +answer
```
View the MX DNS records
```
dig -t MX redhat.com +noall +answer
```
View only the NS DNS records
```
dig -t NS redhat.com +short
```
View all DNS records
```
dig -t ANY redhat.com  +noall +answer
```
View only the IP of the A record
```
dig redhat.com +short
```
View the URL of the given IP (reverse lookup)
```
dig -x 209.132.183.81 +short
```

View TXT record

dig -t TXT yandex-verification.domain.com