#linux #dhcp #dhcpserver #lease #leases *26-07-2025 isc dhcp server will end of life soon. So, the use of #keadhcpserver : [[DHCP Server KEA DHCP]] is recommended.* ### **Viewing Active IP Leases in an ISC DHCP Server** To check which **IP addresses are currently in use** on an **ISC DHCP Server**, follow these steps: --- ### **1. Locate the DHCP Lease File** The **ISC DHCP Server** stores lease information in a file. On most systems, this file is located at: `/var/lib/dhcp/dhcpd.leases` --- ### **2. View the Lease File** To inspect all recorded leases, run: `cat /var/lib/dhcp/dhcpd.leases` This will display **all** lease records, including **expired, released, and active leases**. --- ### **3. Filter Only Active Leases** To find **only active leases**, use: `grep "lease " /var/lib/dhcp/dhcpd.leases | grep -B 1 "binding state active"` - The output will show **IP addresses** and their **status**. - Each lease includes: - **IP address** - **MAC address** - **Lease times** - **Binding state (e.g., active)** --- ### **4. Automate the Process with a Script** If you frequently check for active leases, you can create a simple **Bash script** to automate it. #### **Example: Script to List Active Leases** ``` #!/bin/bash echo "Active DHCP Leases:" grep "lease " /var/lib/dhcp/dhcpd.leases | grep -B 1 "binding state active" ``` Save this as **`check-leases.sh`**, then make it executable: `chmod +x check-leases.sh` Run it anytime with: `./check-leases.sh` --- ### **5. Generate a More Readable Report** For a **clearer overview**, use **`awk`** to extract **IP addresses and MAC addresses**: `awk '/lease / {ip=$2} /hardware ethernet/ {print ip, $3}' /var/lib/dhcp/dhcpd.leases` This will output: ``` 192.168.1.100 00:1A:2B:3C:4D:5E 192.168.1.101 11:22:33:44:55:66 ``` --- 🚀 **With these steps, you can efficiently check which IP addresses are assigned and in use on your DHCP server!** Zie ook [[DHCP Server ISC, Installing Configuring]] Zie ook [[DHCP Server ISC, Reserve IP Address]] Zie ook [[DHCP Server ISC, Stop and Start]] Zie ook [[Windows, DHCP Server Export and Import, PowerShell]]