Redundant / Load Balancing VPN tunnel with 4 routers

RouterOS Forwarding Protocols
1

Hi,

i have the following setup:

                                     +----------------------------+
                                     |  LTE Fallback Telefonica   |
                                     |                            |
+-------------------+        +-------+------+  DSL ISP B   +------+---------+       +-------------------+
|                   |        |              +--------------+   Router B     +-------+                   |
| Redundant virtual |        |              |              +----------------+       |                   |
| juniper switch    +--------+  Internet    |                                       |     HP Switch     |
|                   |        |              |  DSL ISP A   +----------------+       |                   |
|                   |        |              +--------------+   Router A     +-------+                   |
++-+----------------+        +-------+------+              +------+---------+       +-------------------+
 | |                                 |                            |
 | |  +-------------+                |  LTE Fallback Vodafone     |
 | +--+ Router C    |                +----------------------------+
 |    +-------------+
 |
 |    +-------------+
 +----+ Router D    |
      +-------------+

The left side is hosted i a Data Center. We have some public subnets there and we would like to router on of this subnets to the right side of the image. My question is what is probably the best solution to load balance use both DSL uplinks but have redundancy i case of a failure.

My first idea was to create 4 L2TP tunnels:

  1. Router A => Router C
  2. Router A => Router D
  3. Router B => Router C
  4. Router B => Router D

but then i am lost how i should continue. An other idea i head was to use OSPF, but i am not shure if this can help me with this setup.

Do you have ideas?

2

Hi
tunnels sound like a plan, you then could talk ospf on those tunnels and between routers A+B and C+D.
In order to get your upstream in the datacenter to make connectivity redundant you would need to speak some routing protocol there too, usually BGP might be an option, alternate you can form VRRP, but load-balancing might not be achievable then.
And the very same is true for your systems using routers A+B at your site, either do some routing-protocol and enable your systems to support ECMP routing (equal cost multi path).

Regards
hk