UpLink
Athens office line
198.51.100.7
41ms
checked 1 min ago
Link monitoring
An office or ISP connection watched from both ends, so a filtered port and a dead line never read the same.
Included on every plan.
PlansFreeProBusiness
| What breaks | hostnag |
|---|---|
| An ISP link dropsthe public address from several locations, by ping or a TCP port, confirmed by a ping from an internal device | Yes |
| hostnag: external and internal | |
On the board
Sample plates of this type, drawn by the board itself.Acme Retail
02Sample dataInbound blockedLink
Warehouse line
198.51.100.22
port filtered, line answers pingfor 14 min
checked 1 min ago
How it works
- 01
The site's public address
The public IP or hostname of the site's router or gateway, plus the port to reach it on (443 by default).
- 02
hostnag reaches it externally
By ping, by a port, or both, from the group's locations. With both, a port that fails everywhere the ping answers reads as inbound blocked, not down.
- 03
Turn on the internal ping
A heartbeat the device on the far end calls on its own. When the port fails and the device keeps calling, the line is up and something is filtering it.
- 04
Five verdicts, one word each
Up, degraded, link down, inbound blocked, internal silent. Only link down raises an alert that pages anyone.
What you'll be told
What you get told
- Link
[Critical] Office link is down
Port 443 unreachable from US East. Last error: connect_failed: ECONNREFUSED.
- Link
[Warning] Inbound blocked on Office
The site is online (an internal device is pinging) but port 443 is filtered on the way in. Check the firewall or the ISP's CGNAT.
- Link
[Warning] Public IP changed for Office
Office now pings from 198.51.100.20 (was 203.0.113.8). A new lease from the ISP, or failover to a backup line.
Sample alerts, rendered by the same code that writes your email and Slack messages.
Settings
- Target
- public IP or hostname
- Reached by
- ping, a port (443 by default), or both
- Internal ping
- optional heartbeat, its own expected interval and grace
- Public IP change
- raised as a Changed event
- Interval
- 5 min on Free, 1 min on Pro and Business
Questions
What is the difference between inbound blocked and link down?
Inbound blocked means the external test is refused while the internal device keeps pinging; link down means neither side is heard from.
Do I need to install anything on the internal device?
No. It calls the ping URL on its own schedule, the same as a heartbeat; or a Beacon already in that network pings for it.
Related
Read
How to monitor a private host with a Beacon: one readable script, run by your own schedulerWatch an intranet host or an internal certificate from inside your network with one plain script, scheduled by cron, launchd or Task Scheduler.Ping is not uptime monitoring: what an ICMP reply proves, and why a failure needs a second witnessAn ICMP reply proves a machine is there. A TCP connect on the right port is the first real test, and a failure needs a second place to confirm it.How to monitor an office internet link from both ends, so a filtered port and a dead line read differentlyReach the gateway from the internet and have a device inside check in, so a filtered port, a dead line and a new public address each read differently.
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