LB2120 failover

[beachmat]

I was looking at the LB2120 as a possible 4g failover option for our wired internet connection. Am I right in thinking that in order for that feature to work with an existing router, that router must have a second WAN port with failover support? The manual doesn't really talk about this and I can't see how it could work with a router with only 1 WAN port.

Thanks

[plemans]

I think page 20 of the manual goes over automatic failover setup. 

https://www.netgear.com/support/product/LB2120.aspx

From the manual (it then goes over setup): 

The modem provides wireline broadband pass-through with automatic failover support so that you can
connect the modem to an existing DSL, cable, or fiber optics modem (see Connect the Modem to a Wireline
Broadband Modem on page 16). If the wireline broadband connection goes down, the modem can
automatically and seamlessly switch over to the backup Internet connection over the mobile broadband
network for continuous connectivity.This capability is enabled by default.You can manage the IP addresses
that are used in failover detection

[beachmat]

Thanks - I've seen that, but it just says to connect the modem to an ethernet port on the router. In that case, if the main connection goes down, how will the router know to send internet-bound traffic through the LB2120? I'm not clear.

[plemans]

From my reading you'd be going :

Modem---->lb2120 wan port-----lan port---->router (in either ap mode or the router's ip address in the lb2120's dmz). 

By default the lb2120 should just use the modem (hardline) as the data and failover to the mobile connection if the hardline goes down. 

Its if you start making changes that it forces either hardlined or data only. 

The lb2120 would be acting as in the dual wan (hardline or mobile) capacity and feeding your router (if you had a connected one)

[beachmat]

Yes, I understand that the LB2120 has failover enabled by default, and needs a wireline modem connected on the WAN port for that. What I don't quite get is its relationship to an existing router. The manual says you need to set the LB2120 to bridge mode so it isn't routing (fine), but then says to connect its LAN port to "an ethernet port on the router". Presumably they mean the WAN port? So that the LB2120 is sitting between the router and the wireline connection, as you say feeding the router, and not actually doing anything if the wired internet is working? If they mean to connect the LB2120 to a LAN port on the router, I don't get it. 

[plemans]

The lb2120 is effectively just passing data through it if you're going modem----lb2120-----router (its wan port).

If it senses the modem data link fail, it takes over (failover) for supplying your router with data.

That's usually how it works

[beachmat]

Got it, thanks. The manual could have been a little clearer.

[beachmat]

I'm still not quite clear on connecting the LB2120 to a router in bridge mode actually. Does it mean that it is completely transparent, and it is still the router managing the wired internet connection? What about the MAC address - will it be the router's or the LB2120's that the internet provider sees?

[plemans]

I don't have one to test with so I can't say what is going to be seen. 

[rossack]

I have an ADSL modem/router/wifi all in one unit. The modem is also the DHCP server for my network. Since I cant put the LB2120 in between the ADSL WAN port and the Router LAN port, I assume I cant use the failover feature?