Hello
Good catch. Traffic on the wire can never be a mix of IPv4 and IPv6. However the snippet provided here is purely an internal processing/flow logic on the SRX firewalls.
> The example given below is that of a NAT64 - which is IPv6 to IPv4 NAT
> So to achive this both source and destination v6 addresses need to be translated to v4
> As part of the SRX flow processing Dest-NAT happens first
> Therefore the destination gets translated to v4 while source is yet a v6
> Subsequently there is a security policy and source nat lookup
> The snippet you have provided is for creating a source NAT policy while the destination was already translated in the earlier step
> This is where you would see this funny looking combo of source v6 and destination v4
> Here is a link to explain the flow processing on the SRX: https://kb.juniper.net/InfoCenter/index?page=content&id=kb16110
I hope this answers your query. Regards,
Vikas
JTAC-CFTS