# Command `open_firewall` does not work

Symptom

The CLI command `open_firewall` does not work on some nodes.

Cause

SUM is unable to open the firewall in all instances. These include: third-party firewall applications, Linux iptables DROP entries, and firewalls with complex rules.

Action
When the `open_firewall` command does not work, manually open the firewall and then SUM can manage the node.