CCIE SP MPLS FAQ: Running Frame-mode MPLS Across Switched WAN Media
Figure: MPLS Connectivity Across Frame Relay PVCs
Q1: Is it possible to run frame-mode MPLS across an ATM virtual circuit?
Answer: Yes. You can configure an ATM VC so it is treated as a framed interface and so that it uses all the frame-mode label distribution procedures.
Q2. Which two frame-relay encapsulation methods can you use when running MPLS across a frame-relay VC?
Answer: Cisco encapsulation and RFC 1490 (IETF).
Q3. When is it desirable to run frame-mode MPLS across an ATM VC?
Answer: During a network migration or when transit ATM switches do not support MPLS.
Q4. When running MPLS across an ATM forum VC, which encapsulation must you use? Which encapsulation does not function and should not be configured?
Answer: AAL5SNAP encapsulation must be used. AAL5MUX does not function because two separate protocols are exchanged across the same VC.
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