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// Directory & authentication

Port 21846: NetSpeak Corp. Directory Services

Port 21846 is assigned by IANA to netspeak-is (NetSpeak Corp. Directory Services).

21846

How netspeak-is works

Directory & authentication
userdirectorynetspeak-isresponse userdirectorynetspeak-isresponse

The client proves who it is on port 21846 and gets an answer (or a ticket) it can use with other services.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Directory & authentication
01 Security

Is port 21846 dangerous?

We have no specific security note for port 21846. Its risk depends on the program actually listening on it. General advice for directory & authentication services:

  • Keep directory and authentication services on internal networks.
  • Require signing or TLS and disable anonymous queries.
  • Monitor authentication failures for spraying and brute force.
02 Registry

IANA registry entries for port 21846

ServicePortTransportDescriptionReferenceUpdated
netspeak-is 21846 TCP, UDP NetSpeak Corp. Directory Services - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 21846, and is it reachable?

Linux

sudo ss -ltnup 'sport = :21846'      # process listening on 21846
sudo lsof -nP -i :21846

macOS

sudo lsof -nP -i :21846

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 21846 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 21846
netstat -ano | findstr :21846

From another machine

nmap -p 21846 -sV <host>
sudo nmap -sU -p 21846 <host>
nc -zv <host> 21846

Block it in the firewall

sudo ufw deny 21846/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 21846" -Direction Inbound -LocalPort 21846 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 21846 used for?

Port 21846 is assigned by IANA to netspeak-is (NetSpeak Corp. Directory Services).

Is port 21846 TCP or UDP?

Port 21846 is registered for TCP and UDP.

Is it safe to open port 21846?

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. Keep directory and authentication services on internal networks.

How do I check if port 21846 is open?

On Linux run "ss -ltnup 'sport = :21846'", on macOS "lsof -nP -i :21846", and on Windows "netstat -ano | findstr :21846" to see the local process. From another machine, "nmap -p 21846 <host>" shows whether it is reachable.

05 Related
:389 LDAP tcp · udp · high risk :636 LDAPS tcp · udp · moderate risk :88 Kerberos tcp · udp · high risk :3268 Global Catalog (LDAP) tcp · udp · high risk :1812 RADIUS udp · tcp · moderate risk :31 MSG Authentication tcp · udp :49 Login Host Protocol (TACACS) tcp · udp :56 XNS Authentication tcp · udp

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