Default route failover thourgh a second router fails

RouterOS General
1

I have a lab set up with two RB750Gr3 and one LTE router/modem that’s a black box.

Modem has a internet connection and an internal network in the 192.168.0.0/24 sub network. It is meant to emulate an ISP with ether1 on both Routers being a simulated WAN connection.
Routers are connected to the modem through ether1 on each. Both have static IPs: Router A has 192.168.0.41 and Router B has 192.168.0.42.
Both routers are connected to each other thorugh ether 2 using the 172.16.45.0/24 sub network. Router A is 172.16.45.254 and Router B is 172.16.45.253.
Ether3 on both Routers serve their own network with dhcp. Router A has 172.16.43.0/24 and Router B has 172.16.44.0/24. Both are host 254 in their own network.
Router B serves an OpenVPN server on port 192.168.0.42:1194. Router A is connected to said OpenVPN server. Network is 172.16.46.0/24, and A is on 253, while B is on 254.
Finally there’s a last network on ether4 of Router B, using the 172.16.42.0/24 sub network, but there’s nothing in it.

Both Routers have their routing tables set as follows:

Router A:
RB750Gr3_3.rsc (16.3 KB)
Router B:
routesB.png
Now, internal traffic works as I would expect. I can conect from any internal network to any other. For example, I have a pc plugged to Router A in ether3 with 172.16.43.253 as its DHCP obtained IP, and I can enter into Router B’s web interface through its 172.16.44.254 IP. No issues there. The direct cable, and the failover though the OVPN connection work fine as well. I can unplug any of the cables and connections between internal networks keep working. Also, connections to the modem work thourgh ether1 on both Routers, so no issues there.

The problem happens when I unplug the ether1 cable on any single router. It should use the other connection through ether2 as a failover for its default route, but it doesn’t. I lose connection to the modem, and to the internet. This doesn’t make sense to me, so I would appreciate any help or insight on the problem. Thanks!

I’ll leave both routers’ complete rsc scripts as attachments should you require them.
routesA.png
hEX_2 copy.rsc (16.4 KB)

2

So your experiment is to use the WAN connection of the other router when there is a failure?
I’m assuming you are using the LANIPs of the Router from the ISP as two different WAN connections and just fail one or the other correct.

Thus in either case WAN1 on the Router is the direct connected WAN and WAN2 is the other WAN through the other Router?
Do you use R1-ether1 to modem
Do you use R1-ether2 incoming LAN connection from R2 but will act as WAN connection
Do you use R1-ether3 outgoing LAN connection to R2 will act as a WAN connection.

OR
Do you use R1-ether1 to modem
Do you use R1-ether2 incoming WAN connection connection from R2 ( R2 port1 and port3 bridged) { not from LAN }
Do you use R1-ether3 outgoing WAN connection to R2 ( R1 port1 and port3 bridged ) { not from LAN }

Just want to understand the logic of your connection before looking at config.

3

Yes, that’s correct. ether1 in both routers are set up using static addresses and go straight into the LTE modem-router.


By WAN1 and WAN2 you mean the default routes? The 0.0.0.0/0 ones? Then yes, that’s how I have it set up.


Neither. I have it so:
R1-ether1 to modem.
R2-ether1 to modem.
R1-ether2 to R2-ether2.
R1-ether3, R2-ether3, and R2-ether4 have three separate LANs.

I believe this diagram should help ilustrate my setup better than I can explain it with words.
lab-diag.png
Thanks for your time.