Set up outbound NAT at Site B

From the Firewall menu, choose NAT and click on the Outbound tab. Select Manual Outbound NAT rule genera- tion (AON – Advanced Outbound NAT) and click Save. On the next page, click Apply Changes.

A couple of rules are generated automatically but we need to add a NAT entry for Site A’s subnet. Click on the +button.

Enter these values:

Do not NATnot checked 
InterfaceWANUnless using a different interface for the VPN
Protocolany 
SourceType: Network Address: 192.168.10.0/24 Source port: leave emptySite A’s subnet
DestinationType: any Destination port: leave empty 
TranslationAddress: Interface address Port: leave empty Static port: not checked 
No XMLRPC SyncLeave unchecked 
DescriptionSite A 

Click Save and on the next page click Apply Changes.