CCNA Spcor Mpls Sr Questions

The 'include-all' affinity means the tunnel path must include all links that have the specified color attribute. If a link does not have 'red' attribute, it is excluded from the CSPF computation.

EVPN multi-homing uses ESI for identification, DF election to avoid duplicate frames, and aliasing for load balancing.

In downstream unsolicited mode, the router advertises labels for all known prefixes to all neighbors, even if the neighbor did not request them. Liberal label retention keeps all received labels, even if not currently used.

End.DT4 is the SRv6 endpoint behavior that decapsulates the outer IPv6 header and then performs a lookup in the IPv4 VPN table. End.DT6 is for IPv6, and End.DT2U is for L2VPN.

Adjacency SIDs are local to a router and represent a specific link. They are not global and are used for strict path control. They are allocated from a local label range (not SRGB).

In RSVP-TE FRR, facility backup uses a bypass tunnel that can protect multiple LSPs on the same link. In contrast, 1:1 detour creates a separate detour LSP for each protected LSP.

Penultimate Hop Popping (PHP) removes the label before the final hop, and the ingress LSR pushes the initial label.

RSVP-TE FRR offers two protection methods: facility backup (bypass tunnel) and 1:1 protection (detour LSP). Global Repair is not a standard term; Local Protection is used in segment routing.

An Adjacency SID represents a specific link; when a router receives a packet with that label, it pops the label and forwards the packet out of the associated interface, because the Adjacency SID is a 'penultimate hop popping' type of SID.

The DF election is performed using a deterministic algorithm based on the ESI and the list of PEs, with the lowest IP address becoming DF.

Downstream unsolicited means the router sends label bindings without being asked; liberal label retention means it keeps all bindings even if not from the next hop.

The LER (or ingress LSR) imposes a label stack (push operation) on the packet, then forwards it based on the label. It does not swap labels (that's done by LSRs), nor does it pop the label (egress LER does).

End.DT2U is used for L2VPN bridging (EVPN VPWS) and EVPN-IRB uses End.DT2U for bridge domain.

End.DT4 is a SRv6 endpoint behavior that decapsulates an IPv6 packet with an SRH and performs a lookup in the IPv4 VRF table for L3VPN.

RSVP-TE uses PATH messages to establish state and RESV to reserve. To tear down, a PathTear message is sent from the ingress to the egress, or a ResvTear from egress to ingress.

End.DT6 (Endpoint with Decapsulation and IPv6 table lookup) is used for L3VPN over SRv6. It decapsulates the outer IPv6 header and forwards based on the inner IPv6 destination using a specific VRF table.

In RSVP-TE, the headend router sends a PATH message along the explicit route to signal the desired LSP. This message carries the label request, traffic parameters, and the explicit route object (ERO) to each downstream router, which then forwards it hop-by-hop toward the destination. Only after the PATH message reaches the tailend does the tailend respond with a RESV message to actually reserve resources and establish the LSP.

In EVPN-VPWS, the Ethernet Segment Identifier (ESI) uniquely identifies an Ethernet Segment across all multi-homed Provider Edge (PE) nodes. This 10-byte value is used in Designated Forwarder (DF) election and split-horizon filtering to prevent loops when a Customer Edge (CE) is multi-homed to multiple PEs. The ESI is carried in EVPN routes (Type 1 and Type 4) to signal multi-homing membership.

The SRGB defines a range of labels reserved for global segment routing SIDs (e.g., Node SIDs). It ensures that the same label value represents the same prefix across the domain, avoiding label conflicts.

In SR-MPLS, Prefix-SIDs are advertised in IS-IS using TLV 135 (Extended IP Reachability) to carry the prefix and its metric, and TLV 149 (IS-IS Router Capability) to carry the SID/Label Binding sub-TLV, which maps the prefix to a specific label (Prefix-SID). This allows IS-IS to distribute both the prefix reachability and its associated segment identifier in a single protocol update, enabling source routing without LDP or RSVP-TE.

In OSPF, the Extended Prefix TLV (type 1) carries the Prefix SID sub-TLV for segment routing. The Adjacency SID is carried in the Extended Link TLV.

Designated Forwarder (DF) election ensures only one PE forwards traffic to the CE for broadcast/multicast/unknown unicast, and split-horizon prevents a PE from forwarding packets back to the ES from which they were received.

The Adjacency SID is local to the router and represents a specific link; it is typically allocated from the dynamic label range, not the SRGB.

SR-TE reduces state by not requiring per-LSP state on intermediate nodes, supports distributed intelligence via IGP, and does not require a separate protocol like RSVP. However, SR-TE still requires CSPF for path computation, and RSVP-TE also supports fast reroute.

RSVP-TE Fast Reroute uses bypass tunnels to protect links, providing local repair upon failure.

The ingress LSR pushes a new label onto the stack, encapsulating the original IP packet with an MPLS header.

Shared Explicit (SE) style allows multiple senders to share a reservation, which is typical for MPLS-TE where the headend may have multiple LSPs to the same destination.

CSPF computes paths that meet TE constraints such as bandwidth, affinity, and explicit hops while optimizing the path cost.

Shared Explicit (SE) allows multiple senders, each with its own filter spec, but they share the same reservation. Fixed Filter (FF) is per sender. The question likely refers to SE style.

A detour is a 1:1 protection mechanism where a backup LSP is created for each protected LSP, often pre-signaled.

The Ethernet Segment Identifier (ESI) uniquely identifies an Ethernet segment that is multi-homed to two or more PEs.

End.DT6 is the SRv6 endpoint behavior for L3VPN over IPv6, performing decapsulation and lookup in the appropriate VPN routing table.

The Ethernet Segment Identifier (ESI) is a unique identifier for an Ethernet segment that is multi-homed to two or more PEs. ESI is used for DF election and aliasing.