USG/TTB Wires only leased line

[nathan]

This may be a simple answer for some, but my brain isn't with it today....

 

We've just had a new wires only TTB leased line installed, the BT box is now live and I've been sent some IP details (changed slightly).

 

I've been given;

 

WAN Subnet: 212.140.50.34

WAN Subnet Mask: /31

WAN IP: 212.140.50.35

WAN Default Gateway: 212.140.50.34

 

Routers IP Network Number: 212.140.20.220

Routed IP Mask: /30

Routed First Host: 212.140.20.221

Routed Second Host: 212.140.20.222

Routed Third Host: 212:140.20.222

Routed Broadcast Address: 212.140.20.223

 

On the USG i have the following options under static for the WAN;

 

IP Address:

Subnet Mask:

Router:

Preferred DNS:

Alternate DNS:

 

What do i enter? I presume the Routers IP Network Number is the BT box connecting to the fibre?

[Katy]

IP: 212.140.20.221

Subnet: 255.255.255.252

Router: 212.140.20.220

 

Assuming your USG sits between this and your LAN.

 

(On our connection the WAN device is at the other end of the fibre somewhere so a similar model to yours)

[nathan]

Hmmmm, thats what i'm using but it just won't connect. Bit more info;

 

I'm logging into the local USG config which lets me enter WAN details and complete the inform url. I just get a red bar at the top stating "The Gateway is unable to connect to the internet. Please check your configuration."

Edited September 9, 2019 by nathan

[nathan]

I've just spoke to TTB and they said use;

 

IP: 212.140.50.35

Subnet: 255.255.255.254

Router: 212.140.50.34

 

The USG is now saying the subnet mask is invalid?

[Katy]

Oh so looks like your USG sits between the WAN and the routed netblock then, so yeah. I can't imagine that being a valid subnet though as you'd use both addresses as the network and broadcast, leaving zero addresses... No idea sorry

[msi_school]

/31 addresses are valid (rfc3021) but don't always work because some devices don't like them.

 

The unifi forum seems to suggest you cheat https://community.ui.com/questions/USG-PRO-4-with-a-31-subnet/86c07eee-54d6-4406-8fad-ba6417f90a19

 

Reddit says this

[nathan]

I found that link a while ago and i've managed to adopt the USG and enter the WAN details on the controller - stupid thing still won't connect.

[nathan]

After all that, TBB needed to rebuild the circuit and we are live