DHCPv6 Client
What is Port 546?
Port 546 is the client port for DHCPv6, the Dynamic Host Configuration Protocol for IPv6 networks. Defined in RFC 8415, DHCPv6 assigns IPv6 addresses, prefix delegation, DNS server addresses, and other network configuration parameters to IPv6 clients. DHCPv6 operates differently from DHCP for IPv4 — it can work alongside IPv6 Stateless Address Autoconfiguration (SLAAC) or provide full stateful address assignment. The client listens on port 546 and sends requests to servers on port 547. DHCPv6 supports features not available in SLAAC, such as providing DNS search domains, NTP server addresses, and other options. It's essential for enterprise IPv6 deployments that need centralized address management and tracking.
Common Uses
- IPv6 address assignment and management
- DNS and domain configuration for IPv6 clients
- IPv6 prefix delegation for downstream routers
- Enterprise IPv6 address tracking and auditing
Technical Details
Copy-paste commands to check port 546 (DHCPv6 Client) from your terminal
Test connectivity
nmap -p 546 -sU -sV example.com
(echo > /dev/tcp/example.com/546) 2>/dev/null && echo "open" || echo "closed"
Open port in firewall
sudo ufw allow 546/udp
sudo iptables -A INPUT -p udp --dport 546 -j ACCEPT
sudo firewall-cmd --permanent --add-port=546/udp && sudo firewall-cmd --reload
Security Considerations
Like DHCPv4, DHCPv6 lacks built-in authentication, making it vulnerable to rogue server attacks. An attacker can set up a rogue DHCPv6 server to assign malicious DNS servers or redirect traffic. Use DHCPv6 guard on network switches, RA (Router Advertisement) guard, and IPv6 first-hop security features to mitigate these risks.
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