Port 847DHCP Failover
The DHCP Failover protocol is used to synchronize IP address leasing information between two DHCP servers, providing high availability and load sharing in enterprise networks. It allows DHCP services to remain operational even if one server fails, enabling continuous network connectivity for clients..
- transport
- tcp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 9,584
single transport
payload readable on path
registered with iana
caution
rank 498 of 993 · top 50%
Technical Details
what runs on :847The DHCP Failover protocol facilitates communication and synchronization between two DHCP servers managing the same network segment. Its main objective is to maintain consistent lease states, manage load sharing, and provide redundancy. This is critical in enterprise environments, where DHCP address allocation continuity is essential.
The protocol uses a TCP-based session to exchange lease state changes, configuration updates, and keep-alive messages. It supports different failover modes, notably 'load balancing' and 'hot standby'. Load balancing splits lease assignments across servers, while hot standby designates a primary and a secondary server to minimize service interruptions during failover.
Implemented via port 847/TCP, the DHCP Failover protocol is standardized to ensure interoperability between compliant DHCP server implementations. Key data structures include lease ownership states, timers for state transitions, and conflict resolution policies to maintain a coherent lease database between servers.
Security Information
exposure of :847risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
network services averages 3.9 across 604 ports — this one sits 0.1 above.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
tcp
every listening transport is another surface to filter at the edge
security overview
Common vulnerabilities in the DHCP Failover protocol and its implementations include:
- Lack of authentication: As the protocol does not inherently support robust authentication, attackers on the network could potentially spoof failover peers or inject false lease information.
- Cleartext communication: Since the protocol exchanges data unencrypted by default, it is susceptible to eavesdropping and man-in-the-middle (MITM) attacks.
- Denial of Service (DoS): Attackers can potentially disrupt DHCP services by flooding failover connections or corrupting lease state data.
To mitigate these risks:
- Use network-level security controls, such as IPsec tunnels or VPNs, to encrypt communications between failover peers and ensure authentication.
- Restrict access to port 847/TCP to only authorized DHCP servers by configuring firewalls and access control lists (ACLs).
- Monitor failover session logs for anomalies and attempted intrusions.
- Regularly update DHCP server software to patch known vulnerabilities and security flaws.
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0 of 8 encrypted