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Route Distinguishers (RDs) are used in BGP/MPLS VPNs to ensure unique VPN-IPv4 prefixes. Here are the characteristics of RDs:

A. True: An RD is prepended to an IPv4 prefix to form a VPN-IPv4 prefix.

B. True: An RD is used to indicate the VPRN service to which a route update is relevant.

C. True: A unique RD value is assigned to each VPRN service.

The false statement is:

D. False: An RD is a 64-bit value. In reality, an RD is a 96-bit value (composed of a 2-byte Type field and a 6-byte Value field).

ReferencesNokia Border Gateway Protocol Fundamentals, Chapter on Route Distinguishers and VPN-IPv4.

To establish an end-to-end transport tunnel using MP-BGP between PE1 and PE2, the following items are required:

MP-BGP Address Families: MP-BGP address families such as label-ipv4 or label-ipv6 need to be supported on each of the edge routers (PE routers) to handle labeled routes.

Transport Tunnels Between Regions: Tunnels using protocols like RSVP, LDP, or segment routing need to be established between regions to ensure end-to-end connectivity.

Transport Tunnels Within Each Region: Similarly, tunnels using RSVP, LDP, or segment routing need to be established within each region to maintain connectivity.

However, each PE router advertising an IP address as a labeled BGP route is not required for identifying the tunnel endpoint. The tunnel endpoints are typically identified by the transport tunnels established using the above protocols (RSVP, LDP, or segment routing).

ReferencesNokia Border Gateway Protocol Fundamentals, Chapters on MP-BGP and BGP/MPLS VPNs.

When a BGP router receives multiple routes for the same destination, it selects the best route based on several attributes in the following order of preference:

Highest local preference: Routes with the highest local preference are preferred.

Shortest AS_PATH: Routes with the shortest AS path are preferred.

Lowest MED: Routes with the lowest MED are preferred.

eBGP over iBGP: Routes learned via eBGP are preferred over iBGP routes.

Lowest IGP metric to BGP next hop.

Given the routes:

Local preference 100, MED 150, AS Path 65300 65200 (eBGP)

Local preference 100, MED 100, AS Path 63200 (iBGP)

Local preference 200, MED 150, AS Path 65400 63200 (iBGP)

Local preference 200, MED 100, AS Path 63700 (eBGP)

Route 4 has the highest local preference (200), the lowest MED (100), and is learned via eBGP. Therefore, it is the best route.

ReferencesNokia Border Gateway Protocol Fundamentals, Chapter on BGP Route Selection Process.