joaoportela/README.md

Last active October 25, 2025 11:32

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Broadcast DHCP Request

Broadcast a DHCP request (using NMAP). Usefull to check if:

You have multiple DHCP servers in your network.
DHCP servers are responding with expected values (DNS servers, IP range, etc).

Uses a fixed MAC address, which means it does not exaust the IP pool.

Uses NMap script broadcast-dhcp-discover:

Sends a DHCP request to the broadcast address (255.255.255.255) and reports the results. By default, the script uses a static MAC address (DE:AD:CO:DE:CA:FE) in order to prevent IP pool exhaustion. The script reads the response using pcap by opening a listening pcap socket on all available ethernet interfaces that are reported up. If no response has been received before the timeout has been reached (default 10 seconds) the script will abort execution. The script needs to be run as a privileged user, typically root.

Alternatives

For debugging a specific DHCP server, consider using

Raw

dhcp-request.sh

	#! /bin/bash

	DEVICE="${$1:-default}"
	sudo nmap --script broadcast-dhcp-discover -e "${DEVICE}"

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