Port 88: Kerberos
Authentication for Active Directory and other Kerberos realms.
- Port
- 88
- Protocol
- TCP/UDP
- Service
- Kerberos
- Exposure
- Do not expose to the internet
What is port 88 used for?
Domain logins.
Is it safe to expose port 88 to the internet?
Internal only. Never expose domain controllers directly to the internet.
If port 88 seems closed or unreachable
- Check that the Kerberos service is running and listening on port 88, not only on 127.0.0.1.
- Check the firewall on the host itself (Windows Defender Firewall, iptables, nftables, ufw) for a rule that allows TCP 88.
- If the host is behind a router, confirm the forwarding rule points to the correct internal address and that your internet provider does not use carrier-grade NAT.
- Test from outside your own network. A port can be open locally and blocked at the edge, or the other way round.
Using port 88 safely
Treat port 88 as an internal-only service. Reach it through a VPN or an SSH tunnel, restrict it by source address, and keep the software that listens on it patched.
Check whether port 88 is open on your host
The check connects from our server, so it shows what the internet can reach.
Open the port checker