Monitor Internal Servers Behind a Firewall — No Open Ports
Opening a firewall port to let an external monitor reach your internal servers is a tradeoff nobody should have to make. DownWarning's local agent flips the direction of the connection, so your firewall rules never change.
Agent Runs Inside the Firewall
Install the lightweight agent on a machine behind your firewall — no inbound rule, port forward, or DMZ required.
Checks Run Locally
The agent runs HTTP, Ping, and Port checks against your internal servers from the inside, just like a local health check.
Results Go Out, Nothing Comes In
Only encrypted check results travel outbound to DownWarning. Your firewall keeps blocking all inbound traffic, exactly as before.
Why "no open ports" matters
Every inbound port you open for a monitoring tool is a new entry in your firewall rules — and a new thing for your security team to justify during an audit. It's an unnecessary risk for a problem that has a simpler answer.
By running the agent locally and only allowing outbound traffic, DownWarning gives you full visibility into internal servers without adding a single inbound rule to your firewall.
It also removes a recurring maintenance burden: firewall exceptions tend to accumulate over the years and rarely get cleaned up once the original reason is forgotten. Since the agent never requires a new inbound rule in the first place, there's nothing to add to that list and nothing for a future audit to question years later.
This approach works equally well whether "behind the firewall" means a single on-premise rack, a colocated data center, or a home lab — anywhere a machine can make an outbound HTTPS connection, the agent can report results from it. There's no minimum scale or specific network topology required to get started, and nothing to reconfigure later if that topology changes.
Behind-the-Firewall Monitoring FAQ
Does the agent require any inbound firewall rule?
No. The agent only initiates outbound HTTPS connections to report check results. Your firewall's inbound rules do not need to change at all.
What if my internal server has no public DNS record?
That's fine — the agent runs inside the same network as your internal server, so it can reach it by internal hostname or private IP address without any public DNS.
Can I use this instead of a VPN just for monitoring?
Yes. Many teams previously set up a VPN tunnel or bastion host just so an external monitor could reach internal servers. A local agent replaces that entire setup — install it once, and it reports results without needing remote network access.
Will security or compliance teams have concerns about the agent?
Most don't, since the agent never opens an inbound port and initiates only outbound HTTPS connections — the same traffic pattern already allowed for software updates and telemetry. It's typically an easier sign-off than a new VPN tunnel or firewall exception.