CCNP SP MPLS FAQ: The Evolution of MPLS
Q1. What are the MPLS applications mentioned in this chapter?
Q2. Name three advantages of running MPLS in a service provider network.
Answer: The advantages of running MPLS in a service provider network include the following:
- Better integration of IP over ATM
- A network that is running a BGP-free core
- Easy deployment of a peer-to-peer VPN model (MPLS VPN)
- One unified network infrastructure
- Optimal flow of traffic
- Traffic engineering enables the steering of traffic through the network on a path different than the least cost path computed by the dynamic routing protocol
Q3. What are the advantages of the MPLS VPN solution for the service provider over all the other VPN solutions?
Q4. Name the four technologies that can be used to carry IP over ATM.
- RFC 1483
Q5. Name two pre-MPLS protocols that use label switching.
Q6. What do the ATM switches need to run so that they can operate MPLS?
Q7. How do you ensure optimal traffic flow between all the customer sites in an ATM or Frame Relay overlay network?
Figure : Non-Fully Meshed Overlay ATM Network
Q8. MPLS can function using two different modes. What are they?
Q9. When using frame-mode MPLS, where is the label header carried within the frame?
Q10. Describe the format of an MPLS label header.
20 bits label
3 bits EXP field
1 bit S
8 bits TTL field
Q11. In a LAN environment, how does the receiving router identify an MPLS packet?
Q12.: List three different actions an MPLS LSR can perform on a labeled packet when running in frame-mode.
Pop—Removes the top label and forwards as either an IP or MPLS labeled packet.
Swap—Replaces the top label with another value.
Push—Places another label or labels on the top of the label stack.
Aggregate—The egress LSR has to perform additional L3 lookup in its IP forwarding table to successfully forward the packet.
Untag—Similar to Pop, but the result of the Pop operation is an unlabeled IP datagram. This operation is used on egress circuits toward non-MPLS nodes.
Q13. Name two label-distribution protocols used in conjunction with unicast destination-based routing.
Tag Distribution Protocol (TDP).
Label Distribution Protocol (LDP).
Q14. Which label distribution method does a frame-mode implementation use?
Q15. Which label allocation method does a frame-mode implementation use?
Q16. Which label retention method does a frame-mode implementation use?
Q17. How is penultimate hop popping requested through the use of TDP or LDP?
Q18. Because IP packets cannot be exchanged directly between two adjacent
Q19. What is an LC-ATM interface?
Q20. Which label-distribution method is utilized across an LC-ATM interface?
Q21. Which label-allocation method does a cell-mode implementation use?
Q22. Which label retention method does a cell-mode implementation use?
Q23. What is the benefit of using VC-merge?
Q24. Why are labels not distributed to upstream neighbors without having received a label mapping from a downstream neighbor?