Port 1812 (RADIUS): Uses and Security

What uses port 1812

Wi-Fi access points using WPA2/WPA3-Enterprise, VPN concentrators and network switches (802.1X) ask a RADIUS server on UDP 1812 whether a user may connect; accounting records go to 1813. Older equipment may use 1645 and 1646. RADIUS secrets protect only parts of the message, so keep RADIUS traffic on trusted networks or use RadSec (RADIUS over TLS, TCP 2083).

Should port 1812 be open to the internet?

Keep private. Never expose this port to the internet. Keep it on localhost, a private network or behind a VPN or SSH tunnel.

Check what is listening on port 1812

Linux

sudo ss -lunp 'sport = :1812'

macOS

sudo lsof -nP -iUDP:1812

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 1812
netstat -ano | findstr :1812

No output means nothing is listening. If a service should be, check that it is running and which address it binds to: 127.0.0.1 only accepts local connections, 0.0.0.0 or :: accepts them on every interface.

Allow port 1812 from trusted networks only

The examples allow 1812 only from 10.0.0.0/8; replace it with your own private network, office IP or VPN range.

Ubuntu / Debian (ufw)

sudo ufw allow from 10.0.0.0/8 to any port 1812 proto udp
# Close it again:
sudo ufw delete allow from 10.0.0.0/8 to any port 1812 proto udp

RHEL / Fedora / Rocky (firewalld)

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="10.0.0.0/8" port port="1812" protocol="udp" accept'
sudo firewall-cmd --reload

Windows (PowerShell, as administrator)

New-NetFirewallRule -DisplayName "RADIUS 1812/UDP" -Direction Inbound -Protocol UDP -LocalPort 1812 -Action Allow -RemoteAddress 10.0.0.0/8

On AWS, Google Cloud and Azure, also allow the port in the security group or network firewall rules; host firewalls and cloud firewalls are separate.

Test port 1812 from another machine

macOS / Linux

nc -zvu example.com 1812   # UDP has no handshake, so "open" isn't conclusive

Related ports

Port 389 (LDAP): used by LDAP for directory lookups and authentication, including Active Directory.
Port 88 (Kerberos): used by Kerberos authentication, including Active Directory logins.

More network services ports

53 (DNS) , 67 (DHCP server) , 68 (DHCP client) , 123 (NTP) , 135 (Microsoft RPC) , 137 (NetBIOS Name Service) , 179 (BGP) , 636 (LDAPS) . See all ports in the port lookup.

Sources

IANA port registry: 1812

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Frequently asked questions

What is port 1812 used for?

Port 1812 is used by RADIUS for network access authentication. Wi-Fi access points using WPA2/WPA3-Enterprise, VPN concentrators and network switches (802.1X) ask a RADIUS server on UDP 1812 whether a user may connect; accounting records go to 1813. Older equipment may use 1645 and 1646. RADIUS secrets protect only parts of the message, so keep RADIUS traffic on trusted networks or use RadSec (RADIUS over TLS, TCP 2083).

Is it safe to open port 1812?

Never expose this port to the internet. Keep it on localhost, a private network or behind a VPN or SSH tunnel. Allow it only from the networks that need it, as in the firewall examples on this page.

How do I check if port 1812 is open?

On the server, list listening sockets with "sudo ss -lunp 'sport = :1812'" on Linux or "sudo lsof -nP -i :1812" on macOS. From another machine, UDP has no handshake, so a port scan can’t reliably tell whether it is open; test with a real client for the service instead.