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// Databases & caches

Port 25100: IBM Db2 Client Interface - Encrypted

Port 25100 is assigned by IANA to db2c-tls (IBM Db2 Client Interface - Encrypted).

25100

How db2c-tls works

Databases & caches
app:25100#%&@!x9? app:25100#%&@!x9?

The application sends a SQL query to the db2c-tls server on port 25100, which returns rows from its tables. Everything is encrypted: someone on the path only sees unreadable bytes.

Transport
TCP
Exposure risk
not rated depends on the program listening
Encryption
EncryptedTLS or built-in crypto
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Databases & caches
01 Security

Is port 25100 dangerous?

We have no specific security note for port 25100. Its risk depends on the program actually listening on it. General advice for databases & caches services:

  • Bind the service to localhost or a private network, never to a public address.
  • Enable authentication, use per-application accounts and require TLS.
  • Watch for exposed Docker ports: publish them on 127.0.0.1 only.
02 Registry

IANA registry entries for port 25100

ServicePortTransportDescriptionReferenceUpdated
db2c-tls 25100 TCP IBM Db2 Client Interface - Encrypted - 2024-03-05
-25100-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 25100, and is it reachable?

Linux

sudo ss -ltnup 'sport = :25100'      # process listening on 25100
sudo lsof -nP -i :25100

macOS

sudo lsof -nP -i :25100

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 25100 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 25100
netstat -ano | findstr :25100

From another machine

nmap -p 25100 -sV <host>
nc -zv <host> 25100

Block it in the firewall

sudo ufw deny 25100/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 25100" -Direction Inbound -LocalPort 25100 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 25100 used for?

Port 25100 is assigned by IANA to db2c-tls (IBM Db2 Client Interface - Encrypted).

Is port 25100 TCP or UDP?

Port 25100 is registered for TCP.

Is it safe to open port 25100?

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. Bind the service to localhost or a private network, never to a public address.

How do I check if port 25100 is open?

On Linux run "ss -ltnup 'sport = :25100'", on macOS "lsof -nP -i :25100", and on Windows "netstat -ano | findstr :25100" to see the local process. From another machine, "nmap -p 25100 <host>" shows whether it is reachable.

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