Gregg's MOTD

List All MACs on the Local Network

Per the manpage:

The arp tool manipulates or displays the kernel’s IPv4 network neighbor cache. It can add entries to the table, delete one or display the current content. ARP stands for Address Resolution Protocol, which is used to find the media access control address of a network neighbor for a given IPv4 Address.

You can use the arp command to list all of the devices on the local network. It is often useful to find the identities of hidden devices on your network. For example, if you just plugged a Raspberry Pi into your local network and need to find its IP address in order to connect to it via SSH.

# arp -i eth0 -a
? (192.168.1.90) at 42:b9:72:xx:xx:x0 [ether] on eth0
? (192.168.1.70) at 54:04:a6:xx:xx:xd [ether] on eth0
Fios_Quantum_Gateway.fios-router.home (192.168.1.1) at 20:c0:47:xx:xx:x1 [ether] on eth0
? (192.168.1.99) at 34:64:a9:xx:xx:xd [ether] on eth0
? (192.168.1.60) at dc:a6:32:xx:xx:x3 [ether] on eth0

(I’ve masked some of the fields above)

Tags: cli, arp, networking, motd

Netstat

My most frequently used netstat command with parameters for checking port (active internet) connections is:

$ netstat -tulpn

You can also pipe the output to grep to filter for specific ports or addresses.

Here is a brief listing of some of the many options:

$ netstat [options]

Tags: cli, networking, netstat, motd

Find the IP Addresses of KVM Virtual Machines (Command Line)

To find details about the virtual network you can use these commands:

root@slacker:~# virsh net-list
Name State Autostart Persistent
--------------------------------------------
default active yes yes

root@slacker:~# virsh net-info default
Name: default
UUID: 14a90f27-9a85-42ca-b434-6ce6c142690c
Active: yes
Persistent: yes
Autostart: yes
Bridge: virbr0

root@slacker:~# virsh net-dhcp-leases default
Expiry Time MAC address Protocol IP address Hostname Client ID or DUID
------------------------------------------------------------------------------------------------------------
2023-07-22 16:18:45 52:54:00:dd:7b:62 ipv4 192.168.122.216/24 centos7-bbk -

You will find the IP address and hostname listed in the last command’s output.

Optionally, to find the network interfaces’s addresses for a running domain called centos7-bbk:

root@slacker:~# virsh list
Id Name State
-----------------------------
3 centos7-bbk running

root@slacker:~# virsh domifaddr centos7-bbk
Name MAC address Protocol Address
-------------------------------------------------------------------------------
vnet2 52:54:00:dd:7b:62 ipv4 192.168.122.216/24

root@slacker:~#

Tags: cli, kvm, virsh, networking, motd

List TCP Connections Sorted By Host and Most Connections

Assuming your system still has netstat installed (Slackware 15.0 does :^), you can summarize the TCP connections on you host using the following command:

$ netstat -ntu|awk '{print $5}'|cut -d: -f1 -s|sort|uniq -c|sort -nk1 -r

3 52.50.230.xxx
3 104.18.27.xxx
3 104.18.26.xxx
2 205.166.94.xx
2 192.168.1.xx
2 142.251.40.xxx
2 104.18.13.xx
1 74.120.9.xxx
1 66.255.245.xxx
1 54.154.65.xxx
1 52.96.182.xxx
1 45.56.116.xxx
1 45.33.73.xxx
1 34.117.65.xx
1 20.190.135.xx
1 192.168.122.xxx
1 192.168.1.xx
1 172.253.63.xxx
1 162.159.61.x
1 162.125.21.x
1 142.251.40.xxx
1 142.251.32.xxx
1 142.251.16.xxx
1 127.0.0.x

Tags: cli, networking, netstat, motd

Test If a Port is Open with Bash

If netcat isn’t available on your machine and you don’t have the priviledge to install it you can use this trick to test if a port is open or not. It will throw a connection refused message if a port is closed.

$ : </dev/tcp/127.0.0.1/80

And you can use it in a script like this:

(: </dev/tcp/127.0.0.1/80) &>/dev/null && echo "OPEN" || echo "CLOSED"

Tags: cli, networking, bash, motd

Recover Your Wi-Fi Password from Windows CLI

In case you misplaced your wi-fi password you can recover it very easily using 2 commands on Windoze:

Open the Terminal or PowerShell

PS C:\Users\user> netsh wlan show profile

The output will be similar to this. You need to obtain the User Profile of the connection that you’re interested in:

Profiles on interface Wi-Fi:

Group policy profiles (read only)
---------------------------------
<None>

User profiles
-------------
All User Profile : ROUTER21
All User Profile : 4YWD8-5G
All User Profile : 4YWD8

OK, so we know we have 3 profiles. Run the next command with the profile you’re interested in:

PS C:\Users\user> netsh wlan show profile name="ROUTER21" key=clear

You’ll get a bunch of output, but what you’re interested in is the field named Key Content in the Security settings section which holds the wi-fi password in cleartext:

Profile ROUTER21 on interface Wi-Fi:
:
blah blah blah
:
Connectivity settings
---------------------
Number of SSIDs : 1
SSID name : "ROUTER21"
Network type : Infrastructure
Radio type : [ Any Radio Type ]
Vendor extension : Not present

Security settings
-----------------
Authentication : WPA2-Personal
Cipher : CCMP
Authentication : WPA2-Personal
Cipher : GCMP
Security key : Present
Key Content : mywifitpassword
:
blah blah blah
:
:

Tags: cli, wi-fi, networking, motd