Core services ports
8 core services ports: what each one does, its protocol, and whether it is secure by default.
SubnetKit lists 8 core services ports, using TCP/UDP, UDP, TCP. 8 of 8 are formally registered with IANA rather than just a widely followed convention.
1 of the 8 core services 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 |
|---|---|---|---|
| 53 | DNS | TCP/UDP | Domain Name System |
| 67 | DHCP | UDP | DHCP server (BOOTP) |
| 68 | DHCP client | UDP | DHCP client (BOOTP) |
| 111 | RPCbind | TCP/UDP | ONC RPC / rpcbind (portmapper) |
| 123 | NTP | UDP | Network Time Protocol |
| 853 | DNS over TLS | TCP | DNS over TLS (DoT) |
| 2049 | NFS | TCP/UDP | Network File System |
| 5353 | mDNS | UDP | Multicast DNS |
Frequently asked questions
Which ports are in the Core services category?
port 53 (DNS), port 67 (DHCP), port 68 (DHCP client), port 111 (RPCbind), port 123 (NTP), port 853 (DNS over TLS), port 2049 (NFS) and port 5353 (mDNS).
How many core services ports does SubnetKit list?
8, covering TCP/UDP, UDP, TCP. 8 of them are formally registered with IANA.
Are core services ports secure by default?
1 out of 8 are encrypted by default. Check each port's page for its specific encryption status.
Which core services port has the lowest number?
Port 53 (DNS). Port 53 is DNS, which resolves names like example.com into IP addresses. Most lookups use UDP; TCP is used for zone transfers and large responses that do not fit in a single UDP packet.