Configure an External Routed Subnet Scan (Routed Network)

Thanks to Routed Subnet Scan, you can monitor Layer 3 / routed subnets (including VPN-connected networks).

With Routed Subnet Scan, you can discover and monitor, for example:

• Modems and routers located on different subnets
• Networks and devices that are reachable via routing (Layer 3) across subnets
• Multiple sites/buildings connected through a VPN (or other routed links)

How to Configure Routed Network Scan

In order to configure a routed network, once you access your Collector, please:

Secondly, use the “+” button to Add a Routed Network:

At this point, for each subnet, you must specify the following:

• Subnet name
• Network address (starting IP address of the subnet)
• Subnet mask
• Whether you want to use the Advanced Scan via TCP

Once you select “Advanced Scan via TCP“, Domotz will perform discovery scans on the specified subnet using both TCP port-based scanning and ICMP (ping). If this option is not selected, only the ICMP mechanism will be used on that subnet.

As a matter of fact, in some cases, devices cannot be identified (and monitored) via simple ping (ICMP mechanism). In those circumstances, it is recommended to use the Advanced Scan via TCP.

Note: ‘The Advanced Scan via TCP’ is an additional feature that can be used in many case scenarios but can not work as expected in some of them (and this is why it is not enabled by default).

You can experience some unexpected behavior for example if you have a Firewall which is interpreting the Domotz scans as suspicious and act as a honeypot and replying with fake ip addresses.

If this has happened to you please:
– remove all the routed networks you have added to Domotz
– delete all the devices found on those routed networks
– add the routed networks again without enabling the Advanced TCP Scan

In general the standard Routed Network Scan is enough for you to monitor external subnets.

Device monitoring includes those services:

• Network Status
• TCP services available
• SNMP sensors
• Remote connection

Read some examples of configuration on the usage of Routed Subnets (Routed Networks) vs the usage of VLANs (Attached Networks). Read more on our Monitoring Networks with Subnets and VLANs blog post.

In conclusion, if you need to know more about Routed Networks, please refer to our Onboarding guide.