Configure an External Routed Subnet Scan (Routed Network)

2 min

Thanks to the Routed Subnet Scan feature, monitoring up to 8 different Layer 3 subnets of a VPN-connected LAN or other connected/routed subnets is possible.

With the Routed Subnet Scan feature, you can monitor the following:

  • Modems and/or routers on different subnets
  • Networks and network devices routed on different subnets
  • Multiple sites or buildings connected via VPN

How to Configure Routed Network Scan

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

  1. Access the “Device List” section
  2. Click on the “Configure Routed Network Scan” (pencil icon)
“Configure Routed Network Scan” pencil icon

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

Second step: use the "+" button to add a new one

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 a scan (and monitoring) based on TCP
Create a routed network

Once you have selected the “Advanced Scan via TCP“, the scans and monitoring on the created subnet will use the TCP mechanism (scan and monitoring of TCP ports) instead of the ICMP mechanism.

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: If you perform an Advanced Scan via TCP and disable this option, devices that do not “reply” to ICMP messages will be marked offline. You should remove them manually.

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

Note: MAC addresses are not propagated on top of Layer 3. Due to this limitation of Layer 3 information, static IPs are recommended to monitor devices through this feature.

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.

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