With conntrack SNAT communication with PNF fails

When conntrack SNAT is used, communication with the PNF fails.

Steps to reproduce
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Setup requires a pnf to be present.
1)Create a internal vxlan n/w and external flat nw.
2)Create a router and set the gateway
3)Try to ping the vnf

Expected output
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Pnf should be reachable.

Actual output
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ping fails.