Tips on Network

Check whether you have block some services in /etc/hosts.allow or iptables, etc.
http://192.168.0.1/ is the router address
Turn off wireless router and moderm. Start wireless router and wait for 30 seconds, and then start the moderm.

Permanent Change to the File /etc/resolv.conf¶

Notice that the content of /etc/resolv.conf is dynamically managed. Content of the file might change after the host machine is rebooted. Below are some ways to make changes to the file /etc/resolv.conf permanent. (Notice that below are solutions for Linux machines only. Do NOT use any of the solutions below when you are building a Docker image as Docker has its own way of handling DNS.)

Make /etc/resolv.conf immutable.
Update the file /etc/dhcp/dhclient.conf
use resolvconf
more ...

https://kb.isc.org/docs/isc-dhcp-44-manual-pages-dhclientconf

https://www.techrepublic.com/article/how-to-set-dns-nameservers-in-ubuntu-server-18-04/

https://unix.stackexchange.com/questions/128220/how-do-i-set-my-dns-when-resolv-conf-is-being-overwritten

https://unix.stackexchange.com/questions/128220/how-do-i-set-my-dns-when-resolv-conf-is-being-overwritten/163506#163506

https://wiki.debian.org/resolv.conf

https://itsfoss.com/resolvconf-permanent-ubuntu/

https://askubuntu.com/questions/623940/network-manager-how-to-stop-nm-updating-etc-resolv-conf/623956#623956

https://askubuntu.com/questions/157154/how-do-i-include-lines-in-resolv-conf-that-wont-get-lost-on-reboot

https://www.linuxquestions.org/questions/linux-software-2/i-can't-change-file-permission-via-chattr-4175553888/

https://stackoverflow.com/questions/48578108/what-the-differences-between-chattr-i-file-and-chmod-w-file

https://askubuntu.com/questions/1006741/what-is-the-difference-between-chmod-and-chattr

List Network Cards¶

lspci | egrep -i --color 'network|ethernet'

Or you can use

lshw -class network

IP Address¶

To get the your public ip address, use the following simple command.
```
 :::bash
 curl ifconfig.me
```
Or you can use https://www.ipify.org/ which provides A Simple Public IP Address API.
```
 :::bash
 curl https://api.ipify.org?format=json
```
To scan for all ips in a local network, you can use the following command.
```
 arp-scan -l
```
You can specify an device to scan by the option -I.
```
 arp-scan -l -I dev
```
where “dev” is the device name of your net card. For example, if you use wireless network, “dev” is probably “wlan0”.

Network Monitoring¶

vnStat is a console-based tool for monitoring network traffic bandwidth usage. It uses the network interface statistics provided by the kernel as information source. This means that vnStat won’t actually be sniffing any traffic and also ensures light use of system resources.
Tcpdump is a network sniffer tool.

References¶

http://www.linuxandubuntu.com/home/best-network-monitoring-tools-for-linux

https://www.ittsystems.com/linux-network-monitor-tools-and-software/

https://techtalk.gfi.com/the-top-20-free-network-monitoring-and-analysis-tools-for-sys-admins/

https://www.tecmint.com/20-netstat-commands-for-linux-network-management/

https://www.tecmint.com/12-tcpdump-commands-a-network-sniffer-tool/