LB2120 - Both nics on the same network

[JumpMaster]

Hi all,

Is it possible to have the LAN and WAN side of the LB2120 on the same network?  I would only like certain devices to be able to use the LTE backup and to control this by having to set the default gateway to either the Google Wifi router or LB2120.  The LB2120 should forward traffic to the Google WiFi router if the broadband is up and out via the LTE if it it down.  Diagram below.

Thanks!

[schumaku]

No.

To start with and clarify why this is a misconception: These devices LB2120 (and the single port LB11xx) are LTE/4G Modems or LTE4G/ bridges, providing tethering-like an IP address assigned by the mobile provider to one device only. Very similar to a cable modem or a DSL modem. The LB2120 IP configuration available is not for routing purposes - it's only used as a in-band access, nice link layer/L3 trick to "capture" the traffic from/to this address from the Internet traffic flowing through the device.

[JumpMaster]

Hi @schumaku

Thanks for replying but your advice seems incorrect.  The device has the ability to failover between a fixed internet provider and an LTE connection.  From the manual

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.

My question is whether the LAN and WAN connection can be on the same network.

Thanks,

Kev

[schumaku]

I have not even talked of the failover - which works as designed, preferring either broadband or LTE/4G - if implemented exactly as it's in the documentation. 

The problem does start here: Already the first connection and config idea you have in mind can't work - the LAN subnet direct to the LB2120. Once again for the records: The LB2120 is _not_ a NAT router. As the name correctly says - it's a Modem (some of the Netgear documentation does talk of a bridge, technically correct). It does only supply a single IP, either to a single device connected, or to a NAT router WAN interface, as providedfrom the telco or mobile ISP.

[JumpMaster]

Hi @schumaku

Again, from the manual it works in either router mode or bridge mode.

In Router mode, Network Address Translation (NAT) is enabled, the built-in Dynamic Host Configuration Protocol (DHCP) server is enabled to assign a LAN IP address to each connected device, and IP pass-through (IPPT) is disabled.

http://www.downloads.netgear.com/files/GDC/LB2120/LB2120_UM_EN.pdf

Thanks,

Kev

[schumaku]

keV,
Sorry for the false information - appears this NAT router mode is not part of any product descriptions, data sheet, or the like.

Not sure how good Netgear link layer routing engine is when it comes of routing the same subnet (and broadcast domain) on two interfaces.

-Kurt

[JumpMaster]

Thanks for trying to help.  I agree that you wouldn't assume a product called a modem would have NAT.

[JasonN]

Hi JumpMaster,

This will cause an IP conflict. For example, if you set your LAN and WAN to the same IP address then how will you avoid the ip clashing? Also how would you access the LB2120 interface if they both have the same gateway?

If you have the device already, then you can give it a try and confirm. :]

- Jason N

[JumpMaster]

Hi Jason,

-If I had the device I would try it.
-My picture shows the wan and LAN with different IP addresses.
-I would assume only the wan has a gateway as a router uses the wan gateway to pass traffic outside of the lan.

Kev,

[JasonN]

Hi JumpMaster,

I have talked to my colleague and he said that your setup should work with the setup below:

Please let us know if this works for you. :]

- Jason N

[JasonN]

Hi JumpMaster,

I just wanted to check in on you and see if that diagram worked for you.

Please let me know. :]

- Jason N