USG Flex 100 refusing to connect to a Virgin Hub 3 via DCHP and static IP

Inveteratus

Apologies if I've missed an answer to this elsewhere, however being relatively new to networking, a lot of the terminology is new to me.

Essentially, I have a single USG Flex 100 connected from P2 into a Virgin Hub 3. The hub is in it's default configuration so it's address is 192.168.0.1, wireless is disabled as I also have two NWA50AXPRO access points to provide good wireless coverage over the house.

Using Nebula to configure the USG, I initially set it to DHCP to connect to the Hub, though having problems with that, I switched to using a static address of 192.168.0.2. After rebooting the hub, it seems it is failing to see USG.

To alleviate problems, I've reconnected one of the access points directly to the hub, so I've at some WiFi within the house, leaving the other access point connected to the USG.

I have a PC is connected to USG on P2 which connects to the internet via WiFi; I can switch to the ethernet interface and SSH into the USG without issue. I also have a laptop directly connect view ethernet to the Hub.

For reference, the setup is as follows:

hub:

• ip: 192.168.0.1
• netmask: 255.255.255.0
• wifi: disabled
• mode: router
• dhcp: enabled
  • pool-start: 192.168.0.10
  • pool-size: 245
• mtu: 1500

usg-ports:

• p2: wan (wan-group-1)
• p3: lan (lan-group-1)
• p4: lan (lan-group-1)
• p5: lan (lan-group-1)
• p6: lan (lan-group-2)

usg-wan1:

• enabled: yes
• type: static
• ip: 192.168.0.2
• netmask: 255.255.255.0
• gateway: 192.168.0.1
• dns-1: 194.168.4.100
• dns-2: 194.168.8.100
• mtu: 1500

usg-lan1:

• enabled: yes
• lan-port-group: 1
• ip: 192.168.1.1
• netmask: 255.255.255.0
• dhcp: server
  • pool-start: 192.168.1.20
  • pool-size: 200
• dns-1: this gateway
• mtu: 1500

usg-lan1:

• enabled: yes
• lan-port-group: 1
• ip: 192.168.2.1
• netmask: 255.255.255.0
• dhcp: server
  • pool-start: 192.168.2.20
  • pool-size: 200
• dns-1: this gateway
• mtu: 1500

How do I go about connecting the USG to the hub ideally using a static IP address ?

Many thanks!

PeterUK

remove it from Nebula use it in stand alone and see if that works.

PeterUK

It would be recommended to put hub 3 in modem mode.

I do not know why its not working what is dns-1: this gateway?

Do devices to FLEX LAN get a IP? Ping 1.1.1.1 ?

go to maintenance > diagnostics > network tool > ping IPv4 to 1.1.1.1

Maybe the hub 3 DHCP only work for IP's in range of its DHCP pool?

Xydocq

hi @Inveteratus

I have a similar setup, and it works just fine. I didn't change the subnet on the internet box, so it stayed at 192.168.1.0/24. Did you set DMZ to point to the USG?

If your USG isn't connecting to Nebula. Log on to the USG and change the settings there:

You'll need to use 192.168.0.2 and 192.168.0.1 accordingly.

Inveteratus

Thanks @PeterUK for the swift response. To answer your suggestions and questions:

Modem Mode. While I agree, I'd much rather get the USG working first with either a static or dynamic onaddress with the hub in router mode for two reasons - one it ensures I still have internet capability with an access point connected to the hub while the hub's firewall is turned on, and two; given I have a number of ports open notably on my local machine, I'd rather they were protected from the hub or the USG. Bearing that in mind, I've very much of a like minded opinion that the hub should be placed in modem mode - something I will address later down the line.

dns-1: this gateway refers to the text in Nebula's LAN interface configuration modal:

Do devices to flex lan get an ip? Yes, if I connect my PC via DCHP to the firewall, it does get an address, however as the USG is not connected to the Hub, it cannot ping 1.1.1.1 or any other external address.

Does the hub 3 DHCP only work for IP's in range of its DHCP pool? Tricky one to answer. As my Hub's address is 192.168.0.1, and the USG's wan interface static ip set 192.168.02, both with the same netmask of 255.255.255.0, then I'd have assumed they would connect without issue - like any other device in the network connected directly to the hub. With the USG's wan interface in DCHP mode then as it's speaking to the hub, I'd have assumed the hub would indeed by providing an address within it's range which is as stated a pool start of 192.168.0.10 and a size of 245.

@Xydocq - again, thanks for the response.

You said that your internet box is at 192.168.1.0/24, I assume that equates to my hub's ip address being 192.168.0.1. With that mind, given I've set the wan's interface to 192.168.0.2 with the same netmask as the hub - again I feel this should be correct unless my understanding of netmasks is way off.

Did you set DMZ to point to the USG? No, though that is in part as since the USG is not connecting to the hub with either a static or DHCP address, then the hub does not permit me to point the DMZ to and address that is not connected - a sensible precaution I feel!

Your last image shows what I assume is the USG's own internal server however that is not available once the device is configured for Nebula. This is not something I can easily correct, as I've no idea how to restore the native mode for the USG (an no - I neglected to backup the various configs first), and I'm not entirely sure I fancy managing the USG in this way. Nebula does seem a lot simpler.

PeterUK

Well when you 1st setup the USG it must of had internet access?

Did you go to in the USG maintenance > diagnostics > network tool > ping IPv4 to 1.1.1.1 ?

Inveteratus

@PeterUK Quite possibly it did have internet access - however I never used the USG maintenance facility to ping 1.1.1.1 - in fact I never used the USG's own web interface itself - I set it up entirely via Nebula.

PeterUK

Well if your still stuck maybe remove it from Nebula and reset to defaults the USG

Inveteratus

It maybe should be noted that the USG is using firmware version V5.39(ABUH.1), and having compared the startup-config.conf file from the master copy available from portal.myzyxel.com specifically the firmware 5.39 Patch 1 which I believe to be the correct edition, there are negligible differences:

$ diff —suppress-common-lines fw/539ABUH1C0.conf my/startup-config.conf

                                > ! saved at 2025-08-27 10:35:32
                                > ! model: USG FLEX 100
                                > ! firmware version: 5.39(ABUH.1)
                                > !
account pppoe SFP_PPPoE_ACCOUNT <
!                               <
interface sfp_ppp               <
 account SFP_PPPoE_ACCOUNT      <
!                               <
 interface sfp                  <
 interface sfp_ppp              <

So presumably performing a reset will not cuase problems - I must admit to having reset both the hub and the USG on multiple occasions but to no avail.

PeterUK

remove it from Nebula use it in stand alone and see if that works.

Inveteratus

WooHoo — Well after a couple of attempts, that appears to be working - I can indeed ping 1.1.1.1 from the USG's own internal server pages.

Many thanks @PeterUK, standalone-mode it is for now!

Inveteratus

@PeterUK, thanks for the swift response.

Re. modem mode, I'd rather not go down that route until such time as I can setup the USG in the way I want given I already have the odd open port on my local PC - however it's certainly something I wish to investigate.

dns-1: this gateway is essentially exactly what is stated under the LAN interface configuration on Nebula:

Devices cannot ping 1.1.1.1 as the USG is not connected to the Hub, thus no way to communicate to the outside world. This is true for any devices connected to the fireware via ethernet (DHCP), not for those connected to WiFi obviously.

As for the Hub only working for IPs within it's DHCP range, surely having the wan's IP set to either 192.168.0.2/24 OR DHCP when the hub's address is 192.168.0.1 and it grants DHCP from 192.168.0.10 is indeed the same range or am I missing a trick here ?