LUCI associated stations not showing HOST information

Running LEDE 17.01.4 on Linksys WRT3200ACM

The HOST column under Associated Station shows a ? for every connected client.
If I ping a client from the router, the IP address will then appear. I'm not sure how the HOST information gets populated, but the arp tables are not being populated.

IP address       HW type     Flags       HW address            Mask     Device      0x1         0x2         d8:58:d7:00:47:2b     *        br-lan     0x1         0x2         c0:7c:d1:c0:0f:b0     *        br-lan     0x1         0x2         78:4f:43:5d:c6:89     *        br-lan

**that's all it shows

arping hangs for clients connected to radio0 (5GHZ)

root@blue:~#  arping -I br-lan
ARPING from br-lan

I'm not running dnsmasq or odhcpd on the router.

**when using an external dns server, it would be nice if lede could perform a reverse dns lookup and display the actual hostname under in the HOST column, but that's a separate issue...

Screenshot from 2017-12-16 18-57-23

The hostname is ordinarily supplied to the DHCP server during the DHCP process. When the network is configured with static addresses instead of DHCP and you want local hosts resolvable with DNS, you must manually give the hostname / IP table to the DNS server (I think in /etc/hosts).

I'm using an external dns server. At the very least, an IP address should appear in Host column. And it does appear AFTER I ping a client from the router, and the ARP table entry get populated. This is starting to look like a driver/hardware issue, not a LUCI/LEDE issue.

In a "dumb AP" role of taking third parties' traffic from wireless to wired through br-lan, the router OS doesn't need to know IP addresses, and doesn't try to find out. It is a layer 2 bridge that works by MAC addresses.

Only when the router is the source or destination of IP traffic (e.g. pings) then it uses ARP to correlate an IP with its MAC. That is stored in the ARP table which is probably where LuCI looks.