Port 3268: Global Catalog
Port 3268 is the Active Directory Global Catalog port, which lets applications search for objects across every domain in a forest instead of just one domain. It carries the same LDAP protocol as port 389, scoped to the forest-wide catalog.
| Port number | 3268 |
|---|---|
| Service | Microsoft Active Directory Global Catalog |
| Protocol | TCP |
| Category | Windows |
| Default encryption | No |
How do I check whether port 3268 is open?
Port 3268 carries TCP, so a connection either completes its handshake or it does not, which makes the check definitive.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | nc -vz example.com 3268 | A TCP handshake either completes or it does not, so netcat gives a definitive answer in one line. |
| Same check on Windows | Test-NetConnection example.com -Port 3268 | Built into PowerShell. TcpTestSucceeded in the output is the answer; telnet is not installed by default on modern Windows. |
| What is listening locally? | ss -tlnp | grep ':3268 ' | Lists the process bound to port 3268 on Linux. On macOS use lsof -nP -iTCP:3268 -sTCP:LISTEN, on Windows netstat -ano | findstr :3268 |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is port 3268 used for?
Port 3268 is the Active Directory Global Catalog port, which lets applications search for objects across every domain in a forest instead of just one domain. It carries the same LDAP protocol as port 389, scoped to the forest-wide catalog.
Is port 3268 TCP or UDP?
Port 3268 (Global Catalog) uses TCP.
Is port 3268 secure?
Port 3268 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 3268 on my firewall?
Only if you specifically need Global Catalog. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.