Where to find the list of devices with static IPs?

I am running OpenWrt on NanoPi R5C.

I have setup static leases without any problem. I can see the list of active leases in the Web UI.

I have some devices (do not support DHCP) to which static IP must be manually assigned in the configurations thereof.

I have no problem connecting to these devices using the manually assigned IP addresses even though they do not appear in the list of active leases.

It would be very nice to see the list of devices even when IPs are manually assigned.

Is there any way to make devices with manually assigned IPs appear in "Active DHCP Leases" or somewhere else so that I can check whether the device is connected?

Just for clarification: The list of active DHCP leases does not tell you if a host is currently up or down - you just know that the device has obtained a lease in the past and this lease has not timed out yet.

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there aren't any leases, they use static IPs ?

/etc/ethers, not sure if it works for all devices, or only wireless ones.

I understand...
My question is is there any way that I can see the list of devices connected to the router?

Not in realtime.

It is logical that devices with static IP does not appear in the "Active DHCP Leases" because there is no DHCP lease for devices with static IP.

My question is: is there any way to see the list of devices connected to the router?

I added an entry to /etc/ethers and "readethers" option is enabled in DHCP settings but my device with manually assigned IP does not appear anywhere(I don't even know where to look).

It does not have to be in realtime.

Any list would suffice....

The ARP table is a map of IP to MAC for any device which has sent a packet to or through the router. It doesn't have a well defined expiration though. Finding a potentially live device in the ARP table should be followed up with a ping to confirm that it is still live.

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You can see a list of IPv4/v6 Neighbouts by going to Status > Routing in LuCi, or by running ip neigh at the command line. But neither list is going to necessarily be 100% up to date and accurate as hosts connect and disconnect.

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Looks like "IPv4 Neighbours" is good enough for me.

Thank you.

In addition to the passive ip neigh that krazeh mentions, and if you're only looking for IPv4, then an active scan of the address range is possible with nmap:

nmap -sn

The problem already starts with the definition of 'connected', ethernet is a peer-to-peer network - for quite some situations the router doesn't even need to be involved here. Think two clients with static addresses talking to each other, but not the internet - knowledge about these systems won't go beyond the first switch that provides the (direct-) connection between them. Admittedly, most modern operating systems tend to be chatty, both towards the network itself (things like zeroconf) and the internet, but relying on the router to know about everything just doesn't work.

Similar situations happen for modern mobile devices, which tend to agressively enter sleep mode for considerable amounts of time. Are those connected or aren't they?

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