It turns out that Site B also has internal subnets of 10.3.0.0.
Site B's 10.3.0.0 don't need to communicate down the VPNs, but Site C has a need to communicate with Site B. Hence it won't route properly if we send Site C down the VPN as 10.3.0.0.
There are potentially others sites coming online with similar problems.
So basically I was trying to establish if it was possible at Site A to NAT Site Cs range before sending onto Site B (communication is always initiated from Site C). When I look in ASDM it asks for the originating interface as part of the NAT parameters. In this case it would be the Outside, but given the traffic is going back out of that interface (albiet down a VPN) I'm just not sure if this is possible.
Sorry not an ideal setup, but I have taken it over and for various reasons we can't have to hub & spoke the VPNs.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...