Hello,
Proxy-ID and Traffic selector both of them do identical function:- Define set of traffic that can go over tunnel.
With proxy-ID, a single VPN (bound to a tunnel interface) can have a single Local Subnet & single Remote Subnet.
If there are multiple subnets on each side of a route based VPN, since single tunnel interface can have single set of remote and local subnet, the solution used to become complex involving multiple tunnel interface and/or routing-instances with FBF.
But with introduction of traffic selector in a route based VPN, this complexity is gone. You create a single VPN (bound to a tunnel interface) and configure permitted subnets under traffic selector.
For more information, you can refer links below:
https://kb.juniper.net/InfoCenter/index?page=content&id=KB28820
Regards,
Rushi
