Registered · Cross-platform

5666 Nagios NRPE

TCP Unofficial
UDP
SCTP
DCCP

What it is

Nagios Remote Plugin Executor.

When / why

Agent-based monitoring checks. Restrict to the monitoring server.

Protocol status detail

TransportStatusMeaning
TCP Unofficial Not assigned by IANA, but standardized, specified, or widely used on this port.
UDP Not applicable for this transport.
SCTP Not applicable for this transport.
DCCP Not applicable for this transport.

Port range

Registered (1024–49151). Assigned by IANA on request; usable without elevated privileges on most systems.

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Firewall rules for port 5666

Copy-ready inbound rules for the active transports. Replace every <source> placeholder with the specific host, subnet, or CIDR that should reach this port.

ufw

sudo ufw allow proto tcp from <source> to any port 5666

Allow TCP 5666 (Nagios NRPE). Replace <source> with the network/host that should reach it.

firewalld

sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="5666" protocol="tcp" accept'

Allow TCP 5666 (Nagios NRPE) from <source>. Run 'firewall-cmd --reload' afterwards.

nftables

nft add rule inet filter input ip saddr <source> tcp dport 5666 accept

Allow TCP 5666 (Nagios NRPE). Assumes table 'inet filter' with an 'input' chain.

iptables

sudo iptables -A INPUT -p tcp -s <source> --dport 5666 -j ACCEPT

Allow TCP 5666 (Nagios NRPE). Persist with iptables-save/netfilter-persistent.

Azure NSG

az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-nagiosnrpe-5666 --priority 1000 --access Allow --direction Inbound --protocol TCP --source-address-prefixes <source> --destination-port-ranges 5666

Inbound rule for 5666 (Nagios NRPE). Set <source> to a CIDR; lower priority number = higher precedence.

AWS Security Group

aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=tcp,FromPort=5666,ToPort=5666,IpRanges="[{CidrIp=<source-cidr>}]"

Inbound TCP 5666 (Nagios NRPE). Replace <source-cidr> (e.g. 10.0.0.0/16).

GCP firewall

gcloud compute firewall-rules create allow-nagiosnrpe-5666 --direction=INGRESS --action=ALLOW --rules=tcp:5666 --source-ranges=<source-cidr> --network=<network>

Ingress rule for 5666 (Nagios NRPE). Scope with --source-ranges and optionally --target-tags.

Windows netsh

netsh advfirewall firewall add rule name="Allow Nagios NRPE 5666/TCP" dir=in action=allow protocol=TCP localport=5666 remoteip=<source>

Inbound TCP 5666 (Nagios NRPE). Set remoteip to a host/subnet; 'any' is discouraged.

Windows PowerShell

New-NetFirewallRule -DisplayName "Allow Nagios NRPE 5666/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 5666 -RemoteAddress <source>

Inbound TCP 5666 (Nagios NRPE). Replace <source> with a host or subnet.

Rules are generated only for transports marked active for this port. They default to an inbound allow with an explicit source placeholder — never any. Review direction, scope, and rule precedence before applying in production.