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Port 1813 (RADIUS accounting)

RADIUS accounting messages (session start/stop, usage).

Registered (user) port, 1024-49151 UDP Directory and authentication Do not expose to the internet

Port 1813 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

What port 1813 is used for

RADIUS accounting messages (session start/stop, usage).

Security: should port 1813 be open?

Do not expose to the internet. Same restrictions as 1812.

IANA assignment

Service nameProtoDescriptionAssigneeReference
radius-acct TCP RADIUS Accounting - RFC 2866
radius-acct UDP RADIUS Accounting - RFC 2866

Check what is listening on port 1813

Linux: UDP 1813
sudo ss -ulnp 'sport = :1813'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1813
Windows (Command Prompt)
netstat -ano | findstr :1813
Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 1813

Test it from outside

UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1813

Block port 1813 in the firewall

ufw
sudo ufw deny 1813/udp
iptables
sudo iptables -A INPUT -p udp --dport 1813 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1813 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1813' -Direction Inbound -Protocol UDP -LocalPort 1813 -Action Block

Related ports

1812RADIUS authentication49TACACS+1811scientia-sdb1814tdp-suite1815mmpft

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.