Port 161: SNMP
Monitoring and managing network devices.
- Port
- 161
- Protocol
- UDP
- Service
- SNMP
- Exposure
- Do not expose to the internet
What is port 161 used for?
Polling routers, switches and servers for statistics.
Is it safe to expose port 161 to the internet?
SNMP v1/v2c use a community string sent in clear text. Use SNMPv3, restrict by source, and never leave the default community.
If port 161 seems closed or unreachable
- Check that the SNMP service is running and listening on port 161, not only on 127.0.0.1.
- Check the firewall on the host itself (Windows Defender Firewall, iptables, nftables, ufw) for a rule that allows UDP 161.
- If the host is behind a router, confirm the forwarding rule points to the correct internal address and that your internet provider does not use carrier-grade NAT.
- Test from outside your own network. A port can be open locally and blocked at the edge, or the other way round.
Using port 161 safely
Treat port 161 as an internal-only service. Reach it through a VPN or an SSH tunnel, restrict it by source address, and keep the software that listens on it patched.
Check whether port 161 is open on your host
The check connects from our server, so it shows what the internet can reach.
Open the port checker