20000 DNP3 / UserminDNP3 SCADA protocol; also Usermin.
Power/utility SCADA control. Strictly segment OT networks.
| Transport | Status | Meaning |
|---|---|---|
| TCP | Yes | Assigned by IANA and 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. |
Registered (1024–49151). Assigned by IANA on request; usable without elevated privileges on most systems.
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Copy-ready inbound rules for the active transports. Replace every <source> placeholder with the specific host, subnet, or CIDR that should reach this port.
sudo ufw allow proto tcp from <source> to any port 20000Allow TCP 20000 (DNP3 / Usermin). Replace <source> with the network/host that should reach it.
sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="20000" protocol="tcp" accept'Allow TCP 20000 (DNP3 / Usermin) from <source>. Run 'firewall-cmd --reload' afterwards.
nft add rule inet filter input ip saddr <source> tcp dport 20000 acceptAllow TCP 20000 (DNP3 / Usermin). Assumes table 'inet filter' with an 'input' chain.
sudo iptables -A INPUT -p tcp -s <source> --dport 20000 -j ACCEPTAllow TCP 20000 (DNP3 / Usermin). Persist with iptables-save/netfilter-persistent.
az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-dnp3usermin-20000 --priority 1000 --access Allow --direction Inbound --protocol TCP --source-address-prefixes <source> --destination-port-ranges 20000Inbound rule for 20000 (DNP3 / Usermin). Set <source> to a CIDR; lower priority number = higher precedence.
aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=tcp,FromPort=20000,ToPort=20000,IpRanges="[{CidrIp=<source-cidr>}]"Inbound TCP 20000 (DNP3 / Usermin). Replace <source-cidr> (e.g. 10.0.0.0/16).
gcloud compute firewall-rules create allow-dnp3usermin-20000 --direction=INGRESS --action=ALLOW --rules=tcp:20000 --source-ranges=<source-cidr> --network=<network>Ingress rule for 20000 (DNP3 / Usermin). Scope with --source-ranges and optionally --target-tags.
netsh advfirewall firewall add rule name="Allow DNP3 / Usermin 20000/TCP" dir=in action=allow protocol=TCP localport=20000 remoteip=<source>Inbound TCP 20000 (DNP3 / Usermin). Set remoteip to a host/subnet; 'any' is discouraged.
New-NetFirewallRule -DisplayName "Allow DNP3 / Usermin 20000/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 20000 -RemoteAddress <source>Inbound TCP 20000 (DNP3 / Usermin). 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.