In which type of MPLS Layer 3 VPN architecture does the backbone service provider offer an MPLS VPN service to customer service providers?

This type of architecture is known as carriers' carrier (CSC).

How are internal routes are advertised between CSC customer sites via the carriers' carrier backbone network?

Internal routes are advertised using any of the regular PE-CE routing protocols.

How are label bindings advertised between CSC PE and CE routers?

Label bindings are advertised using either LDP or BGP.

How are external routes advertised in a CSC architecture?

External routes are advertised directly between customer sites using BGP.

What type of MPLS Layer 3 VPN network architecture is required if a customer VPN has some of its sites connected to one autonomous system but other sites connected to other autonomous systems?

An inter-autonomous system MPLS VPN architecture is required in this case.

What are the three methods of provisioning an inter-autonomous system MPLS VPN architecture?

Using VRF-to-VRF connectivity at ASBRs; using the advertisement of labeled VPN-IPv4 (VPNv4) between ASBRs with MP-eBGP; and using the advertisement of labeled VPN-IPv4 (VPNv4) between route reflectors in different autonomous systems with multihop MP-eBGP.

Describe the label stack that is prepended to packets as they cross inter-autonomous system links in an inter-autonomous system MPLS VPN architecture when using VRF-to-VRF connectivity at ASBRs.

Packets are unlabeled in this case. The peer ASBRs regard each the other as a CE routers.

What is the effect of the no bgp default route-target filter command?

Usually, when a router receives VPN-IPv4 routes with route targets that do not match the import route targets configured within any of its VRFs, the router drops them. The no bgp default route-target filter command ensures that VPN-IPv4 routes are not dropped in this case.

What are the two common methods of supporting IP multicast transport between customer sites in an MPLS Layer 3 VPNs?

The two methods are point-to-point GRE tunnels and MVPNs.

What are the main advantages of using MVPN when compared to point-to-point GRE tunnels?

MVPN is much more scalable than a mesh of point-to-point GRE tunnels; MVPN does not require special configuration within the customer network.