SNMP traffic across an IPsec Tunnel

I am looking to get SNMP traffic to flow across an IPsec tunnel. I know I have to change the source ip in the CLI for this to work properly. My question is, I have been instructed to use a source IP from a local phase 2 selector. This is a route based tunnel so phase 2 is 0.0.0.0/0 on both sides. There is a static route for 0.0.0.0/0 to go out the WAN1 port for the IPsec tunnel. Would I be using the WAN1 interface ip for the source-ip in the CLI, or how would I go about making this change? Thank you.