Authentication ports
7 authentication ports: what each one does, its protocol, and whether it is secure by default.
SubnetKit lists 7 authentication ports, using TCP/UDP, TCP, UDP. 7 of 7 are formally registered with IANA rather than just a widely followed convention.
1 of the 7 authentication ports is encrypted by default; the rest send data in clear text unless wrapped in TLS, SSH, or a VPN.
Click any port below for its full page: what it does, its protocol, and whether it is safe to expose.
| Port | Service | Protocol | What it does |
|---|---|---|---|
| 88 | Kerberos | TCP/UDP | Kerberos authentication |
| 389 | LDAP | TCP/UDP | Lightweight Directory Access Protocol |
| 464 | kpasswd | TCP/UDP | Kerberos password change |
| 636 | LDAPS | TCP | LDAP over TLS |
| 749 | kerberos-adm | TCP | Kerberos administration |
| 1812 | RADIUS | UDP | RADIUS authentication |
| 1813 | RADIUS accounting | UDP | RADIUS accounting |
Frequently asked questions
Which ports are in the Authentication category?
port 88 (Kerberos), port 389 (LDAP), port 464 (kpasswd), port 636 (LDAPS), port 749 (kerberos-adm), port 1812 (RADIUS) and port 1813 (RADIUS accounting).
How many authentication ports does SubnetKit list?
7, covering TCP/UDP, TCP, UDP. 7 of them are formally registered with IANA.
Are authentication ports secure by default?
1 out of 7 are encrypted by default. Check each port's page for its specific encryption status.
Which authentication port has the lowest number?
Port 88 (Kerberos). Port 88 is Kerberos, the ticket-based authentication protocol behind Active Directory logins. Clients contact the Key Distribution Center here to obtain and present tickets.