Simplest dual-WAN setup for LRT224 ?

Question

Hi folks
Hope someone can help with some insight / advice here.
First, some background :
For a while I’ve been using a conventional ADSL modem-router device to connect to my primary ISP, and thereby provide internet connectivity to a number of desktop PCs, laptops and other mobile devices in a small office environment. I plug the “output” (LAN port) of the ADSL modem-router into a switch, and I also plug a dual-band wireless access point (WAP) into the switch to provide wireless access for the mobile devices. Generally this all works fine.
One problem of course is that if/when my ISP goes down - which does happen occasionally - I have no internet. Also, I am starting to need extra bandwidth, and ADSL connectivity has pretty much reached its speed ceiling in my area. So I’ve been looking at ways of providing redundancy and higher speed by having multiple connections, possibly with different technologies and different ISPs. One option is to go with multiple ADSL connections; another (perhaps better) option is to go with a high-speed fixed-wireless (LTE) connection. With LTE, I can easily get over 30Mbps, so I’ve gone with that option for now. FTTH may be an option on the future. Obviously I needed a 2- or 3-WAN router device to do the connection management.
I had a preference for a dual-WAN router that isn’t tied to any particular communication technology (like ADSL, or VDSL) to give a degree of future-proofing for new technologies like FTTH. I prefer modem devices that have a conventional ethernet port as an output, and hence router devices that have ethernet ports for WAN inputs. This eliminates “combined” devices like Draytek’s “Vigor” ADSL+WAN modem-routers, or routers that have provision to connect a USB 3G stick modem for failover. 
While shopping around, I looked at options like the Cisco RV042/043, the Peplink Balance 20/30, and the Belkin/Linksys LRT224. The LRT224 seemed to offer a reasonable compromise between price, features and performance, so I went with it.
Both my CPE devices are combined modem-routers that completely manage the connection to their respective ISPs, presenting me simply with an ethernet port (or ports) for connection to my local LAN. Specifically, I’m using a D-Link DSL-2500U ADSL modem (1 LAN port) and a Huawei B593s-601 LTE modem (4 LAN ports). Both include the usual functions such as DHCP server, NAT, firewall etc. Previously I’d always give the ADSL modem a fixed IP, and then it let it handle DHCP for the whole of the downstream network. So far, so good.
My requirements for now are pretty straightforward :
- Simple failover operation, ie if one ISP (WAN) goes down, the router should transparently and quickly re-route traffic to the other ISP.
- Load-balancing, ie the ability to apportion traffic between the two ISPs according to a number of different algorithms. Ideally I would want to see options like : equal traffic (bytes) per ISP, % traffic split (eg 60:40), pro-rata split based on connection speed or latency, etc etc ..
- Ability to log into the ‘Web control panel for any of the three devices (LTE modem, ADSL mode, or dual-WAN router) directly from the office LAN without unplugging or re-cabling anything.
- I've no need to use the VPN functionality on the LRT224 at the moment, though that might come later.
Here’s where I need some input and help :
So far, the only way I’ve been able to get this all to work together is as follows :
1) Set up the ADSL modem with a fixed IP of 192.168.1.1 and let it do DHCP on a range like 192.168.1.50/149.
2) Set up the LTE modem with a fixed IP of 192.168.2.1 and let it do DHCP on a range like 192.168.2.50/149.
3) Set up the LRT224 to get WAN-side IP’s from the upstream devices on both WAN1 and WAN2.
4) Set the LRT224 in “Gateway” mode.
5) Set up the LRT224 with a fixed IP of 192.168.0.1, and to issue downstream DHCP IP addresses in the range 192.168.0.50/149.
 What I've noticed in trying to get this all to work is the following:
6) This only works (and gives visibility of all 3 devices) when the two modem devices are on different subnets (like 192.168.1.x and 192.168.2.x). Trying to put them both on the same subnet as the downstream side (all on 192.168.0.x) just doesn't work, or one device is not visible.
7) This only works with the LRT224 in "Gateway" mode, even though "Router" mode seems more fitting.
The setup given above (1 through 5) does work, and gives a situation like the following :
Failover works OK, and I can see any of the three edvices from the office LAN by connecting to any of the assigned IPs.
However, the problem is that the throughput really sucks.
If I connect the LTE modem (only) direct into the office LAN, I get in excess of 20Mbps downlink speed. However, when connecting via the LRT224, I don't even get half that speed, even if the LRT224 is in simple failover mode and the ADSL modem is turned off or out of the picture.
Given that the LRT224 isn't "processing" the packets at all, and there's no VPN overhead, I find it hard to understand why it sucks up over 50% of the throughput. Also, the reviews I read on the LRT224 listed throughputs in the hundreds of Mbps, so this really shouldn't even be a factor. Also, having the LRT224 eat half the throughput partly defeats the one object (higher speed).
So my question is : Is the above setup really the way to do what I want ? Or is there a better way ? The upstream arrangements with dual DHCP on different subnets seems overly complex. Is there a simpler way with PPoE, or PPTP, etc ?
What might I be doing wrong ?
Any input or advice would be much appreciated.
Thanks

Answer 1

Thanks for the suggestions, guys; although I've pretty much covered all of those things.
For info :
1) The router came with firmware v1.0.0.9 (Nov 25, 2013 - the initial release), but I have updated it to the latest v1.0.2.06 (Mar 28, 2014). (This is the third release in 4 months, so it seems Linksys is working fairly actively on LRT2x4 firmware).
2) I have the "Maximum Bandwidth" figures (reached at Configuration / System Management / Bandwidth Management) set to the appropriate values, including a maximum downstream value of 61 440kbps (60Mbps) for the WAN port to which the LTE modem is connected. My understanding, though, is that the LRT224 doesn't DO anything with this information unless there are one or more bandwidth management policies set. (My understanding may be wrong, and the manual isn't much help). I have no bandwidth management policies set.
3) I did try disabling all of the firewall rules as suggested by Flybyknight - no improvement.
One interesting (and unintended / undesired) consequence of my setup is that I can only "see" the configuration pages (web interfaces) for both upstream modems (ADSL and LTE) when the router is in "Load Balance" mode. If it is in "Failover" mode and the primary WAN is up, then I can't see the modem on the secondary (failover) WAN. I assume this is because traffic is only being routed to the active WAN port.
I guess my uncertainty is more about the upstream setup, ie the way in which the upsream-facing WAN ports on the LRT are configured to talk to the downstream-facing LAN ports on the respective modems.
The user guide for the LRT224 is really poor, unfortunately. It doesn't explain the actual workings of the various features at all. For instance, it does not explain what the ACTUAL working of "load balance" is. Does the device route the same amount of traffic (bytes) to both WAN ports, or does it do so in proportion to their configured speeds ? Proper explanations for these features are really indispensable! Belkin/Linksys, are you listening ??