Essential Bash Networking Tasks and Exercises
1.
Display IP Address Information:
Write a Bash script to display the IP address information for all network interfaces.
Code:
#!/bin/bash
# Script to display IP address information for all network interfaces
# Using ifconfig command to display IP address information
ifconfig
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh
eth0 Link encap:Ethernet HWaddr b4:2e:99:a3:ff:d2
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::3b0d:ddbc:ab1e:7095/64 Scope:Unknown
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Unknown
UP LOOPBACK RUNNING MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Explanation:
In the exercise above,
The ifconfig command is used to display the IP address information for all network interfaces on the system. When executed, it shows details such as the interface name, IP address, subnet mask, and more.
2.
Display Network Routing Information:
Write a Bash script to display the network routing table.
Code:
#!/bin/bash
# Script to display network routing information
# Using netstat command to display network routing table
netstat -r
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface default 192.168.0.1 255.255.255.255 U 0 0 0 eth0 192.168.0.0 * 255.255.255.0 U 0 0 0 eth0 192.168.0.101 * 255.255.255.255 U 0 0 0 eth0 192.168.0.255 * 255.255.255.255 U 0 0 0 eth0 224.0.0.0 * 240.0.0.0 U 0 0 0 eth0 255.255.255.255 * 255.255.255.255 U 0 0 0 eth0 127.0.0.0 * 255.0.0.0 U 0 0 0 lo 127.0.0.1 * 255.255.255.255 U 0 0 0 lo 127.255.255.255 * 255.255.255.255 U 0 0 0 lo 224.0.0.0 * 240.0.0.0 U 0 0 0 lo 255.255.255.255 * 255.255.255.255 U 0 0 0 lo
Explanation:
In the exercise above,
The 'netstat' command with the -r option is used to display the network routing table. It shows information about how network packets are routed through the system, including the destination network, gateway, and interface.
3.
Display DNS Information:
Write a Bash script to display DNS (Domain Name System) information.
Code:
#!/bin/bash
# Script to display DNS information
# Using cat command to display contents of /etc/resolv.conf file
cat /etc/resolv.conf
Output:
rg@DESKTOP-3KE0KU4:~$ ./test1.sh # This file was automatically generated by WSL. To stop automatic generation of this file, add the following entry to /etc/wsl.conf: # [network] # generateResolvConf = false nameserver 192.168.0.1
Explanation:
In the exercise above,
The /etc/resolv.conf file contains configuration information for DNS resolution on the system. By using the cat command, you can display the contents of this file, which typically include the IP addresses of DNS servers used by the system.
4.
Check Network Connectivity:
Write a Bash script to check network connectivity by pinging a remote host.
Code:
#!/bin/bash
# Script to check network connectivity
# Prompt the user to input a remote host to ping
read -p "Enter the hostname or IP address to ping: " host
# Using ping command to check network connectivity
ping -c 4 $host
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh Enter the hostname or IP address to ping: google.com PING google.com (142.250.77.174) 56(84) bytes of data. 64 bytes from maa05s17-in-f14.1e100.net (142.250.77.174): icmp_seq=1 ttl=60 time=42.7 ms 64 bytes from maa05s17-in-f14.1e100.net (142.250.77.174): icmp_seq=2 ttl=60 time=42.7 ms 64 bytes from maa05s17-in-f14.1e100.net (142.250.77.174): icmp_seq=3 ttl=60 time=42.3 ms 64 bytes from maa05s17-in-f14.1e100.net (142.250.77.174): icmp_seq=4 ttl=60 time=42.4 ms --- google.com ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3003ms rtt min/avg/max/mdev = 42.306/42.549/42.762/0.279 ms
Explanation:
In the exercise above,
- The script prompts the user to input a hostname or IP address of a remote host to ping.
- The ping command is then used to send ICMP echo requests to the specified host. The -c 4 option limits the ping to 4 requests for simplicity.
5.
Display Listening Ports:
Write a Bash script to display all listening ports on the system.
Code:
#!/bin/bash
# Script to display listening ports
# Using netstat command to display listening ports
netstat -tuln
Output:
Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State Active UNIX domain sockets (w/o servers) Proto RefCnt Flags Type State I-Node P
Explanation:
In the exercise above,
The 'netstat' command with the -tuln options is used to display all listening TCP and UDP ports on the system. This information is useful for understanding which services are actively listening for incoming connections.
6.
Display Established Network Connections:
Write a Bash script to display all established network connections.
Code:
#!/bin/bash
# Script to display established network connections
# Using netstat command to display established connections
netstat -tan
Output:
Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State
Explanation:
In the exercise above,
The 'netstat' command with the -tan options is used to display all established TCP connections on the system. This includes connections that are actively communicating with other hosts.
7.
Check Port Availability:
Write a Bash script to check if a specific port is open on a remote host.
Code:
#!/bin/bash
# Script to check port availability on a remote host
# Prompt the user to input a remote host and port number
read -p "Enter the hostname or IP address: " host
read -p "Enter the port number to check: " port
# Using nc command to check port availability
nc -zv $host $port
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh Enter the hostname or IP address: google.com Enter the port number to check: 6578 nc: connect to google.com port 6578 (tcp) failed: Connection refused nc: connect to google.com port 6578 (tcp) failed: Connection refused
Explanation:
In the exercise above,
- The script prompts the user to input a hostname or IP address of a remote host, as well as a port number to check.
- The 'nc (netcat)' command with the -zv options is then used to check if the specified port is open on the remote host. If the port is open, it will display a success message; otherwise, it will indicate that the port is closed.
8.
Display ARP Cache:
Write a Bash script to display the ARP (Address Resolution Protocol) cache.
Code:
#!/bin/bash
# Script to display ARP cache
# Using arp command to display ARP cache
arp -a
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh /proc/net/arp: No such file or directory
Explanation:
In the exercise above,
The 'arp' command with the -a option is used to display the ARP cache, which contains mappings of IP addresses to MAC addresses for hosts on the local network.
9.
Check Internet Connectivity:
Write a Bash script to check internet connectivity by pinging a well-known external host (e.g., google.com).
Code:
#!/bin/bash
# Script to check internet connectivity
# Using ping command to check connectivity to a well-known external host
ping -c 4 google.com
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh PING google.com (142.250.192.14) 56(84) bytes of data. 64 bytes from bom12s14-in-f14.1e100.net (142.250.192.14): icmp_seq=1 ttl=118 time=58.6 ms 64 bytes from bom12s14-in-f14.1e100.net (142.250.192.14): icmp_seq=2 ttl=118 time=58.3 ms 64 bytes from bom12s14-in-f14.1e100.net (142.250.192.14): icmp_seq=3 ttl=118 time=62.6 ms 64 bytes from bom12s14-in-f14.1e100.net (142.250.192.14): icmp_seq=4 ttl=118 time=58.6 ms --- google.com ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3001ms rtt min/avg/max/mdev = 58.339/59.586/62.670/1.802 ms
Explanation:
In the exercise above,
The 'ping' command with the -c 4 option is used to send ICMP echo requests to the well-known external host (in this case, google.com). This is a simple way to check internet connectivity.
10.
Display Network Interface Statistics:
Write a Bash script to display statistics for all network interfaces.
Code:
#!/bin/bash
# Script to display network interface statistics
# Using ifconfig command to display interface statistics
ifconfig -a
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh
eth0 Link encap:Ethernet HWaddr b4:2e:99:a3:ff:d2
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::3b0d:ddbc:ab1e:7095/64 Scope:Unknown
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
eth1 Link encap:Ethernet HWaddr 00:00:00:00:00:00
inet addr:169.254.241.229 Mask:255.255.0.0
inet6 addr: fe80::6c47:9472:1bbc:b189/64 Scope:Unknown
RUNNING MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Unknown
UP LOOPBACK RUNNING MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Explanation:
In the exercise above,
The 'ifconfig' command with the -a option is used to display statistics for all network interfaces, including information about packets sent and received, errors, collisions, and more.
11.
Check DNS Resolution:
Write a Bash script to check DNS resolution for a domain name.
Code:
#!/bin/bash
# Script to check DNS resolution for a domain name
# Prompt the user to input a domain name
read -p "Enter the domain name to resolve: " domain
# Using nslookup command to check DNS resolution
nslookup $domain
Output:
rg@DESKTOP-3KE0KU4:~$ ./test1.sh Enter the domain name to resolve: google.com Server: 192.168.0.1 Address: 192.168.0.1#53 Non-authoritative answer: Name: google.com Address: 142.250.182.142
Explanation:
- The script prompts the user to input a domain name to resolve.
- The 'nslookup' command is then used to perform DNS resolution for the specified domain name, displaying the corresponding IP address(es) and other DNS-related information.
12.
Display Network Interface Configuration:
Write a Bash script to display the configuration details for a specific network interface.
Code:
#!/bin/bash
# Script to display network interface configuration
# Prompt the user to input a network interface name
read -p "Enter the network interface name: " interface
# Using ifconfig command to display interface configuration
ifconfig $interface
Output:
dt@DESKTOP-3KE0KU4:~$ ./test1.sh
Enter the network interface name: eth0
eth0 Link encap:Ethernet HWaddr b4:2e:99:a3:ff:d2
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::3b0d:ddbc:ab1e:7095/64 Scope:Unknown
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Explanation:
- The script prompts the user to input the name of a network interface.
- The 'ifconfig' command is then used to display the configuration details for the specified network interface, including its IP address, netmask, hardware address, and other settings.
Bash Editor:
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https://www.w3resource.com/bash-script-exercises/networking-tasks.php
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