topic Re: 9800-L AP joining issues in Wireless

9800-L AP joining issues

Netdoofus — Mon, 02 Feb 2026 19:27:16 GMT

I have several 9120AXI AP's that I am trying to get to join up to the WLC. I have others working fine at the moment but these latest few only find and connect up when connected to the same switch as the WLC. Management VLAN for the WLC is 50, I trunk the AP port and set it to 50 as native just like all the other devices (AP3802's) but they will not connect up and just sit flashing red/green with a repeating error of "failed to get ARP entry of WLC IP". If i leave the AP switch port as access with the default VLAN they will find the WLC, join and start broadcasting SSID's but will not hand out IP's to devices that try to join. What am I doing wrong here?

Re: 9800-L AP joining issues

Mark Elsen — Mon, 02 Feb 2026 19:31:26 GMT

- @Netdoofus What type of WLC are you using and what is the software version ?

Re: 9800-L AP joining issues

Stefan Mihajlov — Mon, 02 Feb 2026 21:26:28 GMT

@Netdoofus verify that vlan 50 is allowed on trunk links between switches and DHCP scope for vlan 50 includes the correct DG (Opt 3), as the "failed to get ARP" error indicates the AP cannot resolve path to WLC

Re: 9800-L AP joining issues

Leo Laohoo — Mon, 02 Feb 2026 23:54:24 GMT

If the AP is local, set the switchport config to access port.

If the AP is Flex, the switchport must be Trunk.