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// Network services

Port 847: dhcp-failover 2

Port 847 is assigned by IANA to dhcp-failover2 (dhcp-failover 2).

847

How dhcp-failover2 works

Network services
client:847dhcp-failover2response client:847dhcp-failover2response

The client sends a request to port 847 and the dhcp-failover2 service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Network services
01 Security

Is port 847 dangerous?

We have no specific security note for port 847. Its risk depends on the program actually listening on it. General advice for network services services:

  • Answer only the networks that need the service (no open resolvers, relays or reflectors).
  • UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
  • Disable legacy test services that have no use in production.
02 Registry

IANA registry entries for port 847

ServicePortTransportDescriptionReferenceUpdated
dhcp-failover2 847 TCP, UDP dhcp-failover 2 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 847, and is it reachable?

Linux

sudo ss -ltnup 'sport = :847'      # process listening on 847
sudo lsof -nP -i :847

macOS

sudo lsof -nP -i :847

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 847 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 847
netstat -ano | findstr :847

From another machine

nmap -p 847 -sV <host>
sudo nmap -sU -p 847 <host>
nc -zv <host> 847

Block it in the firewall

sudo ufw deny 847/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 847" -Direction Inbound -LocalPort 847 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 847 used for?

Port 847 is assigned by IANA to dhcp-failover2 (dhcp-failover 2).

Is port 847 TCP or UDP?

Port 847 is registered for TCP and UDP.

Is it safe to open port 847?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Answer only the networks that need the service (no open resolvers, relays or reflectors).

How do I check if port 847 is open?

On Linux run "ss -ltnup 'sport = :847'", on macOS "lsof -nP -i :847", and on Windows "netstat -ano | findstr :847" to see the local process. From another machine, "nmap -p 847 <host>" shows whether it is reachable.

05 Related
:53 DNS tcp · udp · moderate risk :135 MS RPC tcp · udp · high risk :123 NTP udp · tcp · moderate risk :67 DHCP server udp · tcp · moderate risk :111 rpcbind tcp · udp · high risk :9100 Raw printing (JetDirect) tcp · udp · high risk :631 IPP / CUPS tcp · udp · high risk :5353 mDNS udp · tcp · moderate risk

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