IPSEC VPN tunnel and direct traffic between VPN endpoint

[arekkusu]

Hello,

I recently setup an IPSec VPN with a friend, both end running Pfsense.
Getting the tunnel to come up using IKEv2 with matching setting was no problem.

Note a single Phase 2 definition covering the respective local network(s) range was defined:
  Site A: 10.10.0.0/16
  Site B: 10.20.0.0/16

Traffic between host on both side works without issue (when rule is added to allow traffic).
However traffic between the Pfsense boxes is not working I expected:

Using  ping ("Diagnostics > Ping") with default source address I am not able to ping the remote Pfsense private IP. When changing the source address to the LAN it does however work.

Note that both pfsense are connected to multiple network: one WAN and multiple LANs.
It appear that when doing a ping without specifying the source address, it default to using the WAN.

This seems like an odd behaviour to me. I searched a bit but did not managed to find much.
I would appreciate some help or pointer.

• Is an additional Phase 2 recommended to cover traffic the pfsense gateway themselves
• Should I add a static route as a workaround ?

Thanks.