I'm having issues routing traffic thru VPN.

Here's my setup

I have 3 hosts, let's call them A, B and Z

B and Z have a VPN connection in the 10.10.10.x SUBNET A and B have a direct connection in the 10.10.12.x SUBNET

I want to be able to route traffic from A to Z, like :

A <= 10.10.12.254 [LAN] 10.10.12.111 => B <= 10.10.10.152 [VPN] 10.10.10.10 => Z

On host B, i have set up ip_forwarding : net.ipv4.ip_forward = 1

and routing on host B:

[root@hostA: ~]# ip route
10.10.10.10 dev ppp0  proto kernel  scope link  src 10.10.10.152 
10.10.12.0/24 dev eth1  proto kernel  scope link  src 10.10.12.111 
10.10.10.0/24 dev ppp0  scope link 
169.254.0.0/16 dev eth1  scope link 

routing on host A:

[root@hostA: ~]# ip route
10.10.10.0 via 10.10.12.111 dev eth1 
10.10.12.0/24 dev eth1  proto kernel  scope link  src 10.10.12.254 
169.254.0.0/16 dev eth1  scope link 
default via 192.168.1.1 dev eth0

But still not able to ping 10.10.10.10 from host A.

Any idea ? I'm pulling my hairs out.