Explanation
AToM (Any Transport over MPLS) is a framework that supports various Layer 2 transport types over an MPLS network core. One of the transport types supported by AToM is LDP Layer 2 circuit, which is a point-to-point Layer 2 connection that uses LDP for signaling and MPLS for forwarding. LDP Layer 2 circuit can support Layer 2 connectivity without using BGP and can be scalable and efficient by using a single MPLS LSP for multiple VPN connections. The customer can maintain all routing for their private network by using their own CE switches.

Explanation
The configuration shown in the exhibit is for a Layer 3 VPN that connects customer sites that use different AS numbers. A Layer 3 VPN is a type of VPN that uses MPLS labels to forward packets across a provider network and BGP to exchange routing information between PE routers and CE routers. A Layer 3 VPN allows customers to use different routing protocols and AS numbers at their sites, as long as they can peer with BGP at the PE-CE interface. In this example, CE-1 is using AS 65530 and CE-2 is using AS 65531, but they can still communicate through the VPN because they have BGP sessions with PE-1 and PE-2, respectively.

To provide Internet access for VPN-A using CE-1 as the hub CE, you need to do the following:
You must use RIB groups to leak routes between the inet.0 and vpn-a.inet.0 tables on PE-1 and CE-1.
RIB groups are routing options that allow you to import routes from one routing table into another routing table based on certain criteria. In this scenario, you need to configure RIB groups on PE-1 and CE-1 to import Internet routes from inet.0 into vpn-a.inet.0 and vice versa.
Internet traffic from Site 2 takes the path of PE-2 -> PE-1 -> CE-1 -> PE-1 -> GW-1. This is because Site 2 does not have direct Internet access and needs to use CE-1 as its default gateway for Internet traffic. Site 2 sends its Internet traffic to PE-2, which forwards it to PE-1 based on VPN-A routes. PE-1 then sends it to CE-1 based on RIB group import policy. CE-1 then sends it back to PE-1 based on its default route pointing to GW-1. PE-1 then forwards it to GW-1 based on RIB group import policy again.

Explanation
To provide Internet access for the hosts at Site 1, you need to configure static routes in the main routing instance on PE-1 that point to the VPN-A.inet.0 table as the next hop. This allows PE-1 to forward traffic from the Internet to CE-1 using MPLS labels and vice versa. You need to configure two static routes: one for the
10.1.2.0/24 prefix that represents the private network of Site 1, and one for the 203.0.113.1/32 prefix that represents the public IP address of CE-1.