In an MPLS Layer 3 VPN, do CE routers exchange routing update directly with other CE routers or with connected PE routers?

CE routers exchange routes with connected PE routers.

How do PE routers store customer routing and forwarding information?

PE routers store customer routing and forwarding information in VPN routing and forwarding tables (VRF).

How is customer routing information exchanged between PE routers?

It is exchanged using MP-BGP.

In a simple MPLS Layer 3 VPN, with an MPLS-enabled backbone network where PE routers are not directly connected, how many labels are in the label stack of customer packets as they cross the backbone? What are the functions of those labels?

In a simple MPLS Layer 3 VPN, there are two labels in the label stack as customer packets cross the MPLS-enabled backbone. These labels are the IGP and VPN labels. The function of the IGP label is to transport packets between PE routers, and the function of the VPN label is to identify the correct VRF or outgoing interface on the egress PE router.

How can IGP labels be signaled in an MPLS network?

Using LDP, TDP, or RSVP-TE. TDP is a proprietary protocol, and its use is deprecated.

What is the function of the Route Distinguisher (RD)?

The function of the RD is to disambiguate overlapping IP address space.

What is the function of the Route Target (RT)?

The function of the RT is to control the import and export of customer routes into the appropriate VRFs.

Typically, which two IGPs are used in MPLS networks?

Typically, either OSPF or IS-IS is used in MPLS networks. The reason for this is that these are the only two IGPs that have the extensions necessary for MPLS traffic-engineering support.

Which attribute can be used to prevent routing loops when customer sites are multihomed to the service provider MPLS VPN backbone?

The Site of Origin (SoO) attribute can be used to prevent routing loops.

What are three common methods of provisioning Internet access for MPLS Layer 3 VPN customers?

Using a separate global interface on PE routers; using route leaking between VRFs and the global routing table on PE routers; and using a shared services VPN.