Port 6784 (bfd-lag)

IANA assigns port 6784 to bfd-lag: Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces.

Registered (user) port, 1024-49151 UDP

Port 6784 is normally used over UDP; the checker tests TCP only, so a "filtered" result does not mean the UDP service is down.

IANA assignment

Service nameProtoDescriptionAssigneeReference

bfd-lag UDP Bidirectional Forwarding Detection (BFD) on Link Aggregation Group (LAG) Interfaces IESG RFC 7130

Registry dates for this port: registered 2012-11-08, last modified 2014-01-09.

Linux: UDP 6784

sudo ss -ulnp 'sport = :6784'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6784

Windows (Command Prompt)

netstat -ano | findstr :6784

Windows (PowerShell)

Get-NetUDPEndpoint -LocalPort 6784

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 6784

ufw

sudo ufw deny 6784/udp

iptables

sudo iptables -A INPUT -p udp --dport 6784 -j DROP

nftables

sudo nft add rule inet filter input udp dport 6784 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 6784' -Direction Inbound -Protocol UDP -LocalPort 6784 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.