Fing reports Network netmask (prefix length) is not tuned correctly
My fingbox keeps reporting the following:
Network netmask (prefix length) is not tuned correctly
Home network is too wide: 192.168.4.0/22, up to 1024 devices
Is there a way to fix this on my Eero Pro? I don't see a way for Fing to ignore the alerts.
Code 406: Network netmask (prefix length) is correctly configured
Failure case: Network netmask (prefix length) is not tuned correctly
Network check: information are gathered from your current network
The check verifies that your network subnet mask (or network prefix length) is not oversized. Although networking standards recommend to always prefer multicast and broadcast when searching for networking services and devices, many modern IoT devices have still been using unicast sweeps to find peers: this means that lookup, onboarding, pairing or service usage when you have a big network will make the device lookup for the service on a very big number of possible devices, instead of just 256/512. A good example of this is also Windows workgroup: NetBIOS is unicast, so lookup of other PC and printers in a big network takes much longer. The same happens as well to network monitoring software like Fing, Fingbox, and so on: these apps leverage ARP-sweep or ping or similar, so the time taken by a network discovery is proportional to the network size.
What it means for me
A subnet mask is a number that defines the range of (IP) addresses available within a network. It uses the same format as IP address, but in negative format, e.g. 255.255.255.0 is a typical Class C mask including a range of 256 addresses. An alternate form to express it is as network prefix length, meaning how many bits of the network address are stable: a class C network is /24, meaning that 24 bits, first 3 bytes of the address, are not varying.
How I can fix this
An oversized network is much slower than a correctly sized one. E.g. a home network with dozen devices not being a Class C is definitely not tuned correctly. In order to fix it you don't have to change your local PC configuration but rather login into the router configuration and edit it. To make sure every device gets the new updated configuration you should also power cycle or reconnect all connected devices.