Route non-local subnet through IPSec tunnel

Route non-local remote subnet through IPSec tunnel

Setup:
IPSec tunnel, RB450G/RoS-5.25—RB-450G/Ros5.25, (site-to-site)

Site 1: 10.1.0.0/24
Site 2: 10.2.0.0/22

Traffic routing for all 10.1.0.0/24 and 10.2.0.0/22 works fine.

However, I need to route subnet 10.3.0.0/24 from [Site 1] over the IPSec tunnel into the LAN side of [Site2] and setup a forward rule that will get the traffic to another router, say 10.2.0.11 - which will handle delivery to the 10.3.0.0/24 network.


I’ve tried doing this with a second policy in the IPsec configs at each end:
Like so:

src-address=10.1.0.0/24 src-port=any dst-address=10.3.0.0/24 dst-port=any
protocol=all action=encrypt level=require ipsec-protocols=esp tunnel=yes
sa-src-address=1.2.3.4 sa-dst-address=1.2.3.5
proposal=ipsec-proposal priority=0

But the traffic never hits the LAN side of the RB.

I’m sure I’m missing something, but can’t see what or how to resolve it.
[This would all be a LOT easier if RoS would give us an interface to deal with for IPSec traffic!]

Is there a third router NATing 10.3.0.0/24 network to a 10.1.0.0/24 address before it hits the LAN side of the site1 router?

Though not explicitly described, it was assumed no NAT is occurring.
Let me fill the example out, just to make it clear.


Site 1: 10.1.0.0/24
Site 2: 10.2.0.0/22

In this example: Host 10.1.0.15 is sending traffic to 10.3.0.20

So, to make it explicit:
Traffic from say, 10.1.0.15 to 10.3.0.20

That will come into the 10.2.0.0/22 network via the site-to-site IPSec VPN from the 10.2.0.0/24 network.

It will then get forwarded to 10.2.0.11 [a router] that knows how to get to the 10.3.0.0/2 network.
10.3.0.0/24 is NON local to either [site 1] or [site 2].

So, during this travel, the packet will have a [src addr: 10.1.0.15] and [dest addr: 10.3.0.20]

Replies will follow a reverse path. Assume the return packets will be simpy reversed:
[src addr: 10.3.0.20] and [dest addr: 10.1.0.15]

And the return traffic should get handed back to the RB [it's in the default route for the network] and it has a matching policy like so:

src-address=10.3.0.0/24 src-port=any dst-address=10.1.0.0/24 dst-port=any
protocol=all action=encrypt level=require ipsec-protocols=esp tunnel=yes
sa-src-address=1.2.3.5 sa-dst-address=1.2.3.4
proposal=ipsec-proposal priority=0