Site to Site VPN?

Team,

I`m designing my Production environment solution.

Scenario:

Environment: Production
===============

Datacenter: Australia Southeast

No. of WebRoles : 02

SQL Azure Database (Geo - Replication)

Traffic Manager (Round Robbin)

_______________________

Datacenter: Australia east

No. of WebRoles : 02

SQL Azure Database (Geo - Replication)

Diagram for better understanding: http://imgur.com/a/fbGnn





Questions:

a) Do I need site to site VPN?

I`m using the second datacenter (Australia East) for 2 tasks:
i) Webrole instance to be part of the traffic manager wherein the other webrole is from the southeast datacenter.

ii) SQL Azure database replication (Geo-replication)

Thus do I still need site to site VPN?

b) DO I need to have VNET per Datacenter ? or as it is part of ARM resource manager so only one VNET for all services across datacenter is accepted?



Any pointer will be deeply appreciated.

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Regards, Dematri