CCIE SP MPLS FAQ: MPLS/VPN Architecture Operation

Figure: Basic MPLS/VPN Intranet Topology Structure

Q1. Using the basic MPLS VPN mechanisms, is it possible to have overlapping IP addresses within the same extranet VPN?

Answer: No. During the import process, one or more updates are lost because BGP selects one as the best path to the given

Q2. How can the issue of overlapping IP addresses between different sites in an extranet be resolved?

Answer: Through the use of Network Address Translation (NAT).

Q3.What are the two different formats that can be used for the route distinguisher (RD)?

Answer: ASN:nn and IP Address:nn.

Q4. Does the RD have any special meaning for BGP?

Answer: No. BGP interprets the RD as a sequence of bits that, together with the IP address, make up the VPNv4 prefix.

Q5. How are loops prevented between VPN client sites when these sites are multihomed to the backbone?

Answer: Through use of the Site of Origin (SOO) attribute.

Q6.What type-code is used for the route target within the Extended Community attribute?

Answer: Type-code 0x0002 or 0x0102.

Q7. What must you configure to enable static routing, or routing information learned through RIP version 2 or OSPF to be advertised between PE routers?

Answer: Redistribution between the various routing processes and BGP must be enabled.

Q8. Which specific BGP capability must be supported between PE routers to enable the successful exchange of VPNv4 prefix information?

Answer: Multiprotocol Extensions capability.

Q9. What information is carried within the MP_REACH_NLRI attribute?

Answer: Address family information, next-hop information, and NLRI.

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CCIE SP MPLS FAQ: MPLS/VPN Architecture Operation

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