I have several locations that I would like to monitor the state of the Comcast Cable that is provided to use. I have a firewall that is between the Comcast cable box and our public network users. In the event that Comcast service is down the firewall will change it's state to checking. Is there a way that PRTG can alert me when this state changes from UP to Checking?

Thanks for any guidance you can provide on this.

Article Comments

If the firewall is reachable from within your local network you could monitor the state via SNMP, if supported by the Comcast device.

Another solution might be monitoring a website of the firewall's backend HTTP interface (if available), using PRTG's HTTP Advanced sensor. You could then check the page for certain key words and alter the sensor status dependent on the result of this check.


May, 2011 - Permalink

Yes, I had tried both of those, the HTTP advanced is not an option, but the SNMP is but doesn't work unless the link between the firewall and the Comcast router is down.

I currently have a snmptrafficsensor on the eth1 port of the remote firewall which the Comcast internet runs through for our public LAN. When the Comcast service is lost the traffic flattens out as expected. While that is a good indication there is an issue with our public internet it does not send me an alert.

I also have a ping monitor on the Comcast router. However, this will only tell me if the link between the firewall and the Comcast router is down, while helpful, it is very rare and does not alert me in the event Comcast Internet is down.

Ultimately, what I want is to trap the state received from the firewall (Checking). When the Comcast service goes down the firewall will attempt to re-establish a connection and it's state changes from 'UP' to "CHECKING' when this occurs.

Note: Our UTM Firewall does support SNMP, but the Comcast router does not.


May, 2011 - Permalink

You can simply use a Speed Trigger on the eth1-interface for 0 kbit/s for, say, 5 minutes, and could have a notification this way.


May, 2011 - Permalink