UniFi Express (UX) setup failing: No internet detected, but firmware upgrades work?

Networking & Firewalls
1

Hello everyone,

I am setting up a UniFi Express (UX) and running into a strange issue where it cannot detect an internet connection during setup, even though it seems to have partial connectivity. I would appreciate any hints or troubleshooting advice!

Topology & Setup:

  • Router/Console: UCG-Max

  • Switching: USW-Flex-2.5G → Unmanaged Switch → Windows PC & UX

  • USW-Flex-2.5G Port Config: Active, Switching, Native VLAN 10.0.2.0/24, Tagged VLANs Blocked.

The Issue: Both devices appear normally in the UCG-Max client list. The Windows PC gets IP 10.0.2.195 and has perfect internet access. The UX gets IP 10.0.2.194 and shows active up/down traffic in the console.

However, the UX setup process fails to detect an internet connection, dropping me into the local management interface. Interestingly, the UX can successfully download firmware upgrades, so it clearly has some outbound connectivity.

Troubleshooting Steps Taken:

  • Swapped the network cable.

  • Tried configuring the UX Internet settings to Auto Mode (Failed).

  • Tried Manual DHCPv4 (Failed).

  • Tried Manual Static IP (Failed):

    • IP: 10.0.2.194 / 24

    • Router: 10.0.2.1

    • DNS: Auto

UX Device Info:

  • Network: 9.0.118

  • UniFi OS: 4.0.16

I am a bit stuck on why it can upgrade but not pass the internet check. Thank you in advance for your help!

2

It checks internet by pinging a few sites (I think Google, Cloudflare, UniFi, and Microsoft). Have you blocked ICMP on WAN upstream?

3

Hi,

ICMP is not blocked on the WAN upstream. I checked from my UCG-Max console via SSH, and you can see the echo replies coming back successfully.

Running tcpdump -npi eth4 'icmp and host <public WAN address>' provided these results:

Plaintext

listening on eth4, link-type EN10MB (Ethernet), snapshot length 262144 bytes
18:48:44.913698 IP <public WAN address> > 1.1.1.1: ICMP echo request, id 10776, seq 43482, length 9
18:48:44.922530 IP 1.1.1.1 > <public WAN address>: ICMP echo reply, id 10776, seq 43482, length 9
18:48:45.103491 IP <public WAN address> > 64.233.166.138: ICMP echo request, id 62854, seq 1, length 9
18:48:45.109401 IP <public WAN address> > 64.233.166.102: ICMP echo request, id 62855, seq 1, length 9

Since the UCG-Max can ping out fine, is it possible the UX itself is failing the ping.ui.com check internally before it hits the UCG-Max?

Thanks for the help

4

I check from the debug console of the UX device : ping.ui.com is working

5

If you can upgrade it, what is it on an old version?

6

With the two previous version, I have the same issue.

Really don’t know how to investigate further… This is not an hardware issue, in the debug console I can TCPDUMP…

7

Version 10.5 for network app and 5.1 for OS are current. I would update to those latest versions.