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Port 161: SNMP

Port 161 (UDP) is used by SNMP. Keep this port on private networks and reach it through a VPN or SSH tunnel.

Updated

Port161
ProtocolUDP
ServiceSNMP
Internet exposureDon’t expose to the internet

Port 161 is UDP-only, so the TCP-based Port Checker can’t test it. Use the local commands below.

What is port 161 used for?

Simple Network Management Protocol: monitoring of routers, switches and printers.

Should port 161 be open?

Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel. Default “public” community strings leak device details. Keep SNMP on management networks and use SNMPv3.

See what is listening on port 161

# Linux
sudo ss -ulnp | grep ':161 '

# macOS
sudo lsof -nP -i UDP:161

# Windows (PowerShell)
Get-NetUDPEndpoint -LocalPort 161

Open or block port 161 in a firewall

# Ubuntu / Debian (ufw)
sudo ufw allow 161/udp
sudo ufw deny 161/udp

# Windows (PowerShell, as administrator)
New-NetFirewallRule -DisplayName "Port 161" -Direction Inbound -Protocol UDP -LocalPort 161 -Action Allow

On cloud servers, also open the port in the provider’s security group or network firewall. At home, a service behind a router needs a port-forwarding rule to the device’s local IP.

Port CheckerTest whether a server accepts connections on specific ports — web (80/443), mail (25/587/993), SSH, databases or remote desktop — and see which are open, closed or filtered by a firewall.
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Frequently asked questions

What is port 161?
Simple Network Management Protocol: monitoring of routers, switches and printers.
Is it safe to open port 161?
Don’t expose to the internet. Keep this port on private networks and reach it through a VPN or SSH tunnel.
How do I check if port 161 is open?
Port 161 uses UDP, which a TCP check can’t test. On the server, run ss -ulnp (Linux) or Get-NetUDPEndpoint (Windows) to see if something listens.