Hey can you help me on this:
I am trying to master concepts on BGP. Please see attached diagram and my question in red. Appreciate your help.
BGP provides a lot of tools to implement policies but none can deal with ip source addresses:
you can in your scenario implement a route-map applied inbound to neighbor of ISP1
router bgp 7500
neigh 172.16.1 route-map rise_locpref in
but first of all you need to advertise net 192.168.2.0/24 to have a successful communication
in real world a public ip address prefix is associated/owned by a single AS so a better lab setup would be that of having another AS after the two ISPs and then the problem of route choice becomes evident.
until you have a single router you could use also weight:
or directly on neighbor
neighbor 172.16.1.1 weight 500
this provides preferences to all routes learned by this neighbor
or again using a route-map to set the weight selectively on specific routes
If instead you want to send traffic destined to a netA to ISP1 only when the source is 192.168.2.2 you can only use PBR to do this because BGP makes its own choice of best path regardless of the source address.
Hope to help