MPLS study plan
MPLS · Give each week a clear focus.
8 weeks · About 6 hours per week
MPLS Fundamentals and Architecture & Forwarding Plane, Label Stack Operations and PHP
Explain how a label-switched path differs from a hop-by-hop routed path, and describe the roles of LER, LSR, LSP, and label stack depth in a provider network.
Trace the encapsulation order of a labelled packet (frame header, shim header fields, payload) and state what each shim field carries and who writes it.
Walk through penultimate hop popping and explain why an implicit null label exists and what problem it solves at the egress edge.
Compare label imposition, swap, and disposition and identify which operation occurs at ingress, transit, and egress nodes for a given topology you sketch yourself.
Your checkpoint
A one-page hand-drawn or text-based diagram of a 4-router MPLS domain showing label values, stack depth, and PHP at each hop, plus a 300-word written walkthrough of one packet's journey.
Label Distribution and Signalling Protocols (LDP, RSVP-TE)
Describe how LDP discovers neighbours, forms sessions over TCP, and exchanges label mappings, including the difference between downstream unsolicited and downstream-on-demand distribution.
Distinguish liberal and conservative label retention and ordered versus independent control, and state which combination a typical LDP deployment uses.
Explain the purpose of the label information base versus the forwarding information base and how a received mapping becomes an installed forwarding entry.
Outline RSVP-TE path and reservation messages and contrast its resource reservation model with LDP's topology-driven behaviour.
Your checkpoint
A comparison table covering LDP versus RSVP-TE across discovery, path selection, state, reservation, and failure signalling, with at least six rows filled in from your own notes.
MPLS Layer 3 VPNs (VRF, MP-BGP, Route Targets)
Explain how a VRF separates routing tables on a PE and how the global table differs from a per-VRF table.
Describe the MP-BGP VPN-IPv4 address family, the role of the route distinguisher in making prefixes unique, and how a route target controls import and export.
Trace a packet from a CE through ingress PE, P routers, and egress PE, naming the two labels on the stack and what each one is used for.
Explain how a PE decides which VRF receives an incoming VPN route and what happens when route targets do not match.
Your checkpoint
A worked end-to-end example with two VRFs on two PEs, listing the RD, route targets, advertised VPN-IPv4 prefix, and the exact label stack at each hop.
MPLS Layer 3 VPNs (VRF, MP-BGP, Route Targets) & Label Distribution and Signalling Protocols (LDP, RSVP-TE)
Describe the two-label stack in an L3VPN and explain why the inner label is meaningless to P routers.
Explain how a PE learns the outer transport label toward a remote PE and what breaks if that LSP is missing.
Compare a hub-and-spoke route target design with a full-mesh design and state the import/export rules for each.
Describe what a route reflector does for VPN-IPv4 routes and why it changes the next-hop handling requirements.
Your checkpoint
A written troubleshooting scenario where a customer prefix is missing at one site, listing at least five checkpoints in order (VRF config, export target, BGP advertisement, next-hop reachability, import target).
MPLS Layer 2 VPNs and Pseudowires (LDP, BGP-AD, VPLS) & Traffic Engineering and QoS in MPLS
Explain what a pseudowire is and how a targeted LDP session between PEs carries the VC label and label binding for a point-to-point Layer 2 service.
Describe how BGP auto-discovery and VPLS signalling differ from LDP-based pseudowire signalling, and what problem each solves at scale.
Explain the role of the control word and why MTU and fragmentation matter for Layer 2 payloads carried over MPLS.
Describe the basic building blocks of MPLS QoS: EXP bits, per-hop behaviour, classification at ingress, and queueing at egress.
Your checkpoint
A two-column table contrasting LDP-signalled pseudowires with BGP-AD/VPLS across discovery, signalling, scale, and failure handling, with at least five rows.
MPLS Resilience, Fast Reroute and Protection & Traffic Engineering and QoS in MPLS
Explain the difference between local protection and path protection, and describe how a bypass tunnel protects a facility.
Walk through the fast reroute sequence: detection, local repair, and signalling the failure to the head end.
Describe how RSVP-TE reservations interact with DiffServ treatment of EXP bits under a tunnel, including the pipe and uniform tunnel models.
Explain what makes a backup path loop-free and how a node avoids double-counting bandwidth during protection.
Your checkpoint
A failure walkthrough for a protected LSP: state what happens at the point of local repair in the first 50 ms, then after the head end reconverges, naming every message involved.
Operations, Troubleshooting and Verification & Label Distribution and Signalling Protocols (LDP, RSVP-TE)
List the specific commands or data you would collect first when a customer reports an L3VPN outage, ordered from least to most disruptive.
Explain how to verify an LSP end to end without relying on user traffic, and what each verification step proves.
Describe how to read a label forwarding table to confirm an expected swap or pop and how to detect a stale or missing label binding.
Explain how to isolate whether a fault is in the control plane (label not advertised) or the forwarding plane (label advertised but not installed).
Your checkpoint
A personal troubleshooting checklist of at least ten ordered steps with the expected healthy output described in words for each step, no device screenshots.
Segment Routing and Modern MPLS Evolution & Forwarding Plane, Label Stack Operations and PHP
Explain segment routing over MPLS: what a node segment and an adjacency segment are and how a segment list becomes a label stack.
Contrast segment routing's distributed path control with RSVP-TE's per-LSP state and describe what state is removed from transit nodes.
Describe how prefix segments are advertised and how a controller or head end steers traffic with a segment list.
Revisit label stack operations and explain how the same push, swap, and pop mechanics apply to a segment list at each hop.
Your checkpoint
A 500-word written summary of how one traffic-engineered path is expressed as a segment list and forwarded hop by hop, ending with a short list of what state each transit node holds.
Milestones
Week 2: Can explain, without notes, the full LDP session lifecycle and the difference between an advertised label mapping and an installed forwarding entry.
Week 4: Can draw the two-label L3VPN stack from memory and explain the purpose of the RD, route target, and inner label in one pass.
Week 6: Can describe the fast reroute sequence and the pipe versus uniform QoS model accurately enough to teach them to a colleague.
Week 8: Can compare RSVP-TE and segment routing on state, path control, and failure handling, and state which label stack operations occur at ingress, transit, and egress for a segment list.