Currently the customer has only 1 router and 1 core swicth.
The 2 units of WXC each will act as standalone to load-balance the traffic from remote sites wxc 1800.
Therefore there will run on different IP address but on same subnet.
What shld be the best deployment method FOR 2 WXC ACTIVE-ACTIVE in this scenario with ONLY 1 ROUTER AND 1 SWITCH?
There is option in the WXC to configure the Load Balancing,
In WXC 1800, please goto Compresseion -> Advanced -> Load Balancing.
There you can choose the option Per-destination or Flowbased option to do the Load balancing and achieve the benefit from the Active-Active WXC.
I would suggest you to get in touch with your local Juniper Sales Engineer to get this setup approved for WXC to work with no issues.
I hope this clarifies your queries.
Advanced JTAC Engineer - WX/MFC