I can see all connected devices to my Linux PC with:
cat /proc/net/arp
But this show only the IPv4 addresses and MAC of the connected devices. There is no IPv6 addresses.
How to find the IPv6 addresses of the connected Devices?
asked Jan 9, 2018 at 15:42
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2“I can see all connected devices to my Linux PC” – but you can’t. The ARP cache only contains information about hosts your machine happens to have communicated with. The only way to find most hosts is a network scanner like nmap.– Daniel BJan 9, 2018 at 15:45
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1Do you mean connected in sense that the other devices are on the same network - or connected in sense that there is open active connection between the two?– Marek RostJan 9, 2018 at 16:05
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2 Answers
This is because IPv6 does not use Address Resolution Protocol (ARP) it uses Neighbor Discovery Protocol (NDP).
Using the command ip neighbor will list both ARP cache and discovered IPv6 neighbors.
The simplest command is to list out all connections is the ss | less, but to view only tcp or udp or unix connections use the -t that is,
ss -t
this should show you all IPv4 and IPV6 tcp connections.
To display only IPv4 socket connections use the
-f inetor-4option.ss -tl -f inet or
ss -tl -4
While to display only IPv6 connections use the
-f inet6or-6option.ss -tl6 or
ss -finet6
Or simply for the combined IPv4 and IPv6 neighboring nodes use
ip neighbour
Which will shows the current neighbour table in kernel.
But NOTE: /proc/net/arp doesn't list devices connected to your PC. It shows a list of devices on your subnet for which your PC has done/seen an ARP request for. If you want to see which devices are connected to your PC, then you need netstat or similar (which will automatically show both ipv4 and ipv6 devices). ipv6 doesn't use ARP (it uses NDP)
I hope this helps
