Nokia NRSII 4A0-C04 Set2 [051-100]

Question 1

Question 51:

Which of the following about label modes on the Nokia 7750 SR is FALSE?

A. RSVP uses downstream on demand label distribution mode.

B. LDP uses conservative label retention mode.

C. LDP advertises label mappings to all peers for which it might be a next-hop for a given FEC.

D. RSVP distributes a label mapping for a FEC when it has been requested to do so.

Answer 1

B. LDP uses conservative label retention mode.

Answer Explanation:

This statement is FALSE. RSVP-TE uses downstream unsolicited label distribution mode, not downstream on demand. In downstream unsolicited mode, the egress (downstream) router sends label bindings to upstream routers without waiting for a request. In contrast, LDP can use either downstream on demand or unsolicited depending on configuration.

Question 2

Question 52

This policy is applied on a router as an LDP export policy and an LDP session has been established between this router and its neighboring router. In addition to the FECs learned from its neighbors, what additional FECs will appear in this router’s LIB?

A. All FECs that are in the 192.168.1.0/24 address space.

B. Local FECs that are in the 192.168.1.0/24 address space.

C. All FECs that are not in the 192.168.1.0/24 address space.

D. All FECs except the local FECs that are in the 192.168.1.0/24 address space.

Answer 2

B. Local FECs that are in the 192.168.1.0/24 address space.

Explanation:

The policy applies only to directly connected prefixes that fall under the 192.168.1.0/24 longer filter — meaning it includes 192.168.1.0/25, 192.168.1.128/25, etc., but not 192.168.1.0/24 itself. However, most platforms interpret prefix 192.168.1.0/24 longer as “anything more specific than /24” (e.g., /25 or /26 within the /24). In this context, local FECs that match the longer-than-/24 condition are explicitly exported to the LIB. So the policy affects only local (i.e., directly connected) prefixes.

Question 3

Question 53:

Which of the following about RSVP-TE is FALSE?

A. It supports traffic protection using IGP equal cost paths.

B. It supports CAC to prevent resource overbooking.

C. It supports LSPs with traffic engineering constraints.

D. It supports LSPs that follow the IGP best path.

Answer 3

A. It supports traffic protection using IGP equal cost paths.

Explanation:

RSVP-TE (Resource Reservation Protocol - Traffic Engineering) is a protocol used to set up LSPs (Label Switched Paths) with strict control over routing and resources. It does not support ECMP (Equal Cost Multi-Path) for traffic protection or path setup — RSVP-TE prefers explicitly calculated or signaled paths based on constraints like bandwidth, admin groups, etc.
In contrast, LDP (Label Distribution Protocol) naturally supports ECMP because it follows IGP best paths.

Question 4

Question 54:

LSP 1’s link between routers R3 and R6 has failed, and the RESV state at router R3 has timed out.
Which of the following actions will router R3 initiate?

A. Send a PathTear message towards router R6.

B. Send a PathTear message towards router R1.

C. Send a ResvTear message toward router R6.

D. Send a ResvTear message toward router R1.

Answer 4

D. Send a ResvTear message toward router R1.

Explanation:

When the RESV state times out at router R3 (due to loss of downstream connectivity to R6), router R3 will notify the upstream routers that the reservation is no longer valid. In RSVP-TE, this is done by sending a ResvTear message upstream — in this case, toward the head-end router R1.

A PathTear is typically initiated by the head-end router (R1) to tear down an LSP.

A ResvTear is used by downstream routers to notify upstream routers about reservation failure.

Since the failure occurred after the RESV was established and it has now timed out at R3, the correct response is to tear down the reservation upstream, toward R1.

Question 5

Question 55:

Click on the exhibit. After the lsp-ping command is executed, which of the following best describes the router’s action?

A. MPLS Echo Request packets are sent within the RSVP-TE tunnel that is signaled for “lsp-toR2”.

B. MPLS Echo Request packets are sent within the LDP tunnel that is signaled for Mlsp-toR2.

C. MPLS Echo Request packets are IP-routed to the destination address of “lsp-toR2”.

D. MPLS Echo Request packets are sent to the destination address of “lsp-toR2” over TCP.

Answer 5

A. MPLS Echo Request packets are sent within the RSVP-TE tunnel that is signaled for “lsp-toR2”.

When the lsp-ping command is executed, it triggers an MPLS OAM (Operations, Administration, and Maintenance) operation that tests a specified LSP. The MPLS Echo Request is injected into the RSVP-TE LSP path, not routed via regular IP or TCP. This is done to test the forwarding plane of a specific LSP, not just IP connectivity.

Question 6

Question 56:

Which of the following about IS-IS Traffic Engineering on a Nokia 7750 SR is FALSE?

A. Traffic engineering information is carried in the extended TLVs.

B. Traffic engineering must be enabled on all IP/MPLS routers along the LSP path.

C. Traffic engineering information is stored in the opaque database.

D. Traffic engineering is required for constraint-based LSPs.

Answer 6

C. Traffic engineering information is stored in the opaque database.

Explanation:

On Nokia SR OS, IS-IS Traffic Engineering (TE) information is stored in the TE database, not the opaque database.

Question 7

Question 57:

Which LSA type is used for OSPF-TE?

A. Type 8 LSA — Link Local LSA

B. Type 9 LSA — Link Local Opaque LSA

C. Type 10 LSA — Area Local Opaque LSA

D. Type 11 LSA — AS Opaque LSA

Answer 7

C. Type 10 LSA — Area Local Opaque LSA

Answer Explanation:

OSPF-TE (OSPF for Traffic Engineering) is an extension of OSPF that uses Opaque LSAs to carry traffic engineering information (e.g., bandwidth, link attributes) across the network.

Opaque LSAs include:

Type 9 – Link-local scope

Type 10 – Area-local scope ✅

Type 11 – AS scope

For OSPF-TE:

Type 10 LSAs are the most commonly used, carrying link-state information relevant to TE within a specific area.

This includes:

Link bandwidth

TE metrics

Admin groups (colors)

SRLGs, etc.

Option Review:
A. Type 8 – Used in IPv6 OSPFv3, not relevant to TE.

B. Type 9 – Link-local only, used for directly connected info (not scalable for TE).

C. ✅ Type 10 – Correct for carrying TE info within an area.

D. Type 11 – AS-wide, used less frequently for TE.

Question 8

Question 58:

Which of the following regarding label population is TRUE?

A. Selected labels from the FIB are populated to the LFIB.

B. Selected labels from the RIB are populated to the FIB.

C. Selected labels from the LIB are populated to the FIB.

D. Selected labels from the LIB are populated to the LFIB.

Answer 8

D. Selected labels from the LIB are populated to the LFIB.

Explanation:

The Label Information Base (LIB) stores all received label bindings from LDP, RSVP, or other label distribution protocols.

The Label Forwarding Information Base (LFIB) contains only the labels actually used for forwarding, selected based on the best path in the routing and label tables.

The router populates the LFIB with label entries that correspond to the best forwarding paths, selected from the LIB (in combination with the FIB/RIB).

So, the correct and true statement is that labels from the LIB (after selection) are installed in the LFIB for forwarding.

Question 9

Question 59:

Which of the following is NOT an application of MPLS?

A. Enabling VPNs

B. Enabling traffic engineering

C. Enabling network security

D. Enhancing network resiliency

Answer 9

C. Enabling network security

Explanation:

MPLS (Multiprotocol Label Switching) is primarily used for:
VPNs: MPLS Layer 3 and Layer 2 VPNs are widely deployed in service provider networks.

Traffic Engineering (TE): MPLS-TE allows for explicit path control and bandwidth reservation.

Network Resiliency: Fast reroute and backup LSPs improve availability.

However, MPLS is not inherently a security technology. While it provides isolation (especially in VPNs), it does not encrypt or authenticate traffic, so it’s not considered a network security mechanism.

Question 10

Question 60:

Which of the following fields does NOT appear in the MPLS label header?

A. Label

B. Frame check sequence

C. Traffic Class (previously called Experimental)

D. Time To Live

E. Bottom of stack bit

Answer 10

B. Frame check sequence

Explanation:

An MPLS label header is 32 bits and includes the following fields:
Label (20 bits)

Traffic Class (3 bits; used for QoS/CoS, previously called Experimental)

Bottom of Stack (S bit) (1 bit)

Time to Live (TTL) (8 bits)

A Frame Check Sequence (FCS) is a data link layer function used in technologies like Ethernet, but it is not part of the MPLS label header.

Question 11

Question 61:

What is the possible reason that the label for prefix 192.10.1.2/32 is not active?

A. The router does not have a route to reach the peer 10.10.10.2/32.

B. The router does not have a route to reach the prefix 192.10.1.2/32.

C. The router does not have an export policy defined to export the prefix 192.10.1.2/32 into LDP.

D. The router receives an invalid label for the prefix 192.10.1.2/32 from its peer.

Answer 11

B. The router does not have a route to reach the prefix 192.10.1.2/32.

Answer Explanation:
Let’s analyze the show router ldp bindings output from router R1 (10.10.10.1):

Prefix: 192.10.1.2/32
EgrLbl = 131067 → This means R1 received a label mapping from its peer (10.10.10.2) for this prefix.

Inglbl = (blank) → R1 has not advertised a label to anyone else for this prefix.

Label In Use (U) flag is missing → the label is not active, even though it was received.

What determines label usage?
In LDP:
A label received for a prefix becomes “in use” (U) only if the prefix is reachable via the peer that advertised the label.

If R1 doesn’t have a route in its IGP to reach 192.10.1.2/32, then the label can’t be installed in the forwarding table.

Option Review:
A. ❌ R1 has a label mapping with 10.10.10.2, so it does have a route to the peer.

B. ✅ This is correct — no route to 192.10.1.2/32 means the label is not used.

C. ❌ LDP does not require export policies to install received labels.

D. ❌ The label is valid — it was accepted and stored, just not activated.

Question 12

Question 62:

Which of the following about RSVP-TE summary refresh messages is TRUE?

A. They list the RSVP session names that the router is refreshing.

B. They list the Message IDs that the router is refreshing.

C. They list the Tunnel IDs that the router is refreshing.

D. They list the LSP IDs that the router is refreshing.

Answer 12

B. They list the Message IDs that the router is refreshing.

Explanation:

RSVP-TE uses periodic refreshes of PATH and RESV messages to maintain LSP state. Summary Refresh (as per RFC 2961) improves scalability by reducing overhead.
Summary Refresh Messages do not contain full PATH/RESV messages.

Instead, they list Message IDs, so the receiving router can:

Check if it still has state for those IDs.

Request a full message if it’s missing or inconsistent.

Other options are incorrect because:
A: Session names are not used in the protocol.

C/D: Tunnel IDs and LSP IDs are not referenced in the Summary Refresh message format.

Question 13

Question 63:

If an LSP needs to use an admin group, which of the following configurations is NOT required on the Nokia 7750 SR?

A. Assign an admin group to a MPLS interface.

B. Configure CSPF on the LSP.

C. Configure at least one strict hop on the LSP path.

D. Configure an “include” or “exclude” statement on the LSP path.

Answer 13

C. Configure at least one strict hop on the LSP path.

Explanation:

To utilize admin groups (also called colors or link attributes) in LSP setup on the Nokia 7750 SR:
Admin groups must be assigned to MPLS interfaces (Choice A).

CSPF (Constrained Shortest Path First) must be enabled to consider admin group constraints (Choice B).

Admin group usage requires inclusion or exclusion criteria on the LSP path (Choice D).

However:
Strict hops (C) are not required for using admin groups.

LSPs can be dynamically computed using loose hops or none at all, and CSPF still considers admin groups without strict hop definitions.

Question 14

Question 64:

Click on the exhibit. The partial command output from a Nokia 7750 SR is shown.
Which of the following about this LSP path is TRUE?

A. R4 (10.10.10.4) has established a link protection tunnel.

B. R6 (10.10.10.6) has established a link protection tunnel.

C. R2 (10.10.10.2) has established a node protection tunnel.

D. R1 (10.10.10.1) has not established a node protection tunnel.

Answer 14

D. R1 (10.10.10.1) has not established a node protection tunnel.

Answer Explanation:

Let’s interpret the exhibit:
The Actual Hops section shows the IP addresses of the routers forming the explicit LSP path.

Next to each hop, you see labels and the “@” notation:

@n means node protection is NOT established at that hop.

Record Label shows the label used for each hop in the LSP.

Actual Hop Details:
mathematica
Copy
Edit
-> 10.1.3.1 (10.10.10.1) @ n Record Label: N/A
-> 10.1.3.3 (10.10.10.3) @ n Record Label: 131069
-> 10.3.4.4 (10.10.10.4) @ Record Label: 131069
-> 10.2.4.2 (10.10.10.2) Record Label: 131067
-> 10.2.6.6 (10.10.10.6) Record Label: 131071
Key Observations:
Both R1 (10.10.10.1) and R3 (10.10.10.3) have @n → no node protection.

The lack of @n for other hops implies node protection is either established or not applicable at those points.

Node protection is a form of fast reroute (FRR) where a PLR (Point of Local Repair) can protect against next-hop router failure using a detour.

Question 15

Question 65:

Which of the following regarding the location of an MPLS label is FALSE?

A. The MPLS label value may be carried in an ATM header.

B. The MPLS label value may be carried in a shim header.

C. The MPLS label value may be carried in an OSPF header.

D. The MPLS label value may be carried in a Frame Relay header.

Answer 15

C. The MPLS label value may be carried in an OSPF header.

Explanation:

A – TRUE:
MPLS can operate over ATM networks. In this case, labels are carried in the ATM VPI/VCI fields using the MPLS-over-ATM encapsulation format.

B – TRUE:
The shim header is the most common method of carrying MPLS labels — it’s inserted between Layer 2 and Layer 3 headers.

C – FALSE (Correct Answer):
OSPF headers are routing protocol messages used for IGP topology exchange. They do not carry MPLS labels. MPLS label values are not transmitted in routing protocol headers like OSPF.

D – TRUE:
Like ATM, MPLS labels can be mapped onto DLCI fields in Frame Relay headers under certain legacy deployments.

Question 16

Question 66:

An IS-IS TE enabled router has an interface on a 500 Mbps link and it is configured with a 25% subscription.
If this interface is not used by any LSPs, what value will be shown in the Reservable Bandwidth sub-TLV?

A. 125 Mbps

B. 500 Mbps

C. 625 Mbps

D. 2000 Mbps

Answer 16

A. 125 Mbps

Answer Explanation:

In IS-IS with Traffic Engineering (TE) extensions, the Reservable Bandwidth in the sub-TLV represents the maximum bandwidth available for RSVP-TE LSPs.
This is determined by:
Reservable Bandwidth = Interface Bandwidth × Subscription Percentage
Given:
Physical link speed = 500 Mbps

Subscription = 25% (0.25)

No LSPs are using bandwidth (so nothing is reserved yet)

Calculation:
CopyEdit
500 Mbps × 0.25 = 125 Mbps

So the advertised Reservable Bandwidth is 125 Mbps.

Option Review:
A. ✅ 125 Mbps – ✔ Correct based on 25% of 500 Mbps.

B. ❌ 500 Mbps – Would be true only with 100% subscription.

C. ❌ 625 Mbps – Invalid; exceeds physical capacity.

D. ❌ 2000 Mbps – Way above the actual link bandwidth.

Question 17

Question 67:

The LSP “toR6” is configured with a fully strict path on a Nokia 7750 SR. Which of the following configurations is required to enable fast reroute for this LSP?

A. Enable fast-reroute on all routers along the path. R1, R2, R4, and R6.

B. Enable both link-protection and node-protection on router R1.

C. Enable fast-reroute with either one-to-one or facility mode on this LSP.

D. Enable link-protection only on router R4.

Answer 17

C. Enable fast-reroute with either one-to-one or facility mode on this LSP.

Answer Explanation:

Fast reroute (FRR) in RSVP-TE must be explicitly enabled on the LSP using either one-to-one or facility mode. This configuration allows the router to establish bypass tunnels or detour LSPs in the event of link/node failure. Merely enabling FRR on intermediate routers or applying link/node protection without configuring the LSP’s reroute mode is insufficient.

Question 18

Question 68:

Which MPLS label mode saves label mappings received from all peer LSRs?

A. Conservative label retention

B. Liberal label retention

C. Downstream on demand

D. Downstream unsolicited

Answer 18

B. Liberal label retention

Answer Explanation:

In MPLS, liberal label retention mode means a router retains all label mappings received from all peer LSRs, regardless of whether they are currently used for forwarding. This provides fast convergence in case of IGP changes since alternate labels are already available. In contrast, conservative label retention only keeps labels from the next-hop LSR selected by the routing protocol.

Question 19

Question 69:

An LDP-over-RSVP tunnel is established between PE-1 and PE-2. Which of the following is NOT required to protect the LDP-over-RSVP tunnel?

A. PE-1 requires T-LDP sessions to both ABR-1 and ABR-2.

B. PE-1 requires a full mesh of RSVP-TE LSPs to all routers in area 1.

C. ABR-1 requires T-LDP sessions to all ABRs in area 0.

D. PE-1 requires fast reroute enabled on all RSVP-TE LSPs.

Answer 19

B. PE-1 requires a full mesh of RSVP-TE LSPs to all routers in area 1.

Answer Explanation:

LDP-over-RSVP only requires that PE-1 establish T-LDP sessions with its connected ABRs (ABR-1 and ABR-2), and that those ABRs maintain RSVP-TE LSPs across Area 0 to ABRs on the far side (ABR-3/ABR-4). PE-1 does not need RSVP-TE LSPs to all routers in Area 1, making answer B the correct choice.

Question 20

Question 70:

Consider the following:

• Router R2 is an ABR in OSPF Areas 0 and 1.
• Router R2 advertises the aggregate prefix 10.10.10.0/24 into Area 1.
• Router R1 in Area 0 generates LDP labels for FECs 10.10.10.102/31 and 10.10.10.4/31.
• Router R3 in Area 1 places these FECs in its LIB, but it does not place them in its LFIB.

What can you do on router R3 to make it populate these labels in its LFIB?

A. Disable route summarization on router R3

B. Enable LDP aggregate prefix match

C. Create an import policy to accept these FECs

D. Disable LDP exact match on the specified FECs

Answer 20

B. Enable LDP aggregate prefix match

Answer Explanation:

When a router receives labels for more specific FECs than its IGP routing table (which may contain only a summarized route like 10.10.10.0/24), the LFIB will not install the label mappings unless aggregate prefix matching is enabled. This feature allows the router to associate labels for more specific prefixes with a less specific (aggregate) route, thereby enabling label forwarding.

Question 21

Question 71:

Which of the following commands is used to display the database containing the OSPF-TE LSAs?

A. show router ospf opaque-database

B. show router ospf database

C. show router ospf opaque-lsa

D. show router ospf te opaque

Answer 21

A. show router ospf opaque-database

Answer Explanation:

In Nokia SR OS, OSPF-TE information is carried in opaque LSAs (specifically types 9, 10, and 11). The command show router ospf opaque-database is used to display the database that stores these opaque LSAs, including those relevant to traffic engineering (TE). This command is specifically designed to inspect TE extensions advertised in OSPF for building the TED (Traffic Engineering Database).

Question 22

Question 72:

Which routing protocol cannot be run over an Ipipe?

A. OSPF

B. RIP

C. BGP

D. IS-IS

Answer 22

D. IS-IS

An Ipipe (Infrastructure Pipe) is a type of pseudowire used to transport Layer 2 traffic across an MPLS network. It typically supports Ethernet or TDM traffic and is transparent to higher-layer protocols. Most IP-based routing protocols (such as OSPF, RIP, and BGP) can be encapsulated over Ethernet frames and sent over an Ipipe, assuming there’s IP connectivity. However, IS-IS is a Layer 2 protocol and does not use IP as its transport, making it incompatible with Ipipe transport which operates at Layer 2. Therefore, IS-IS cannot be run over an Ipipe.

Question 23

Question 73:

Which of the following statements is TRUE?

A. An OSPF adjacency can be established on an IES interface.

B. IES allows provider MP-BGP sessions to be extended to customers.

C. An IES service must use static routes in order to communicate with customer networks.

D. An IES interface supports OSPF and IS-IS in passive mode only.

Answer 23

A. An OSPF adjacency can be established on an IES interface.

Answer Explanation:

IES (Internet Enhanced Service) interfaces in Nokia SR OS are Layer 3 interfaces that support IP routing protocols. You can configure OSPF, IS-IS, and BGP directly on IES interfaces to establish routing adjacencies with customer or provider devices. Therefore, OSPF adjacencies can be formed on IES interfaces, making statement A true.

Question 24

Question 74:

On Nokia 7750 SR OS, routing information between the CE and PE can be exchanged using the following methods.

A. ISIS, RIP, OSPF, static routes

B. BGP, ISIS, RIP, OSPF, static routes

C. BGP, RIP, OSPF, static routes, OSPF3

D. ISIS, RIP, OSPF, static routes, OSPF3

Answer 24

C. BGP, RIP, OSPF, static routes, OSPF3

Answer Explanation:
On Nokia 7750 SR OS, the routing protocols supported on the PE-CE interface for exchanging VPN routes include:
BGP – commonly used in MPLS L3VPN for dynamic route exchange (MP-BGP).

RIP – legacy protocol, still supported.

OSPF / OSPF3 – OSPFv2 for IPv4, OSPFv3 for IPv6.

Static routes – always an option for simple environments.

IS-IS is NOT supported on the CE-PE interface** – it is typically a service provider core IGP.

Option Review:
A. ❌ – Missing BGP and OSPF3.

B. ❌ – Includes IS-IS (not used on CE-PE).

C. ✅ – All valid: BGP, RIP, OSPF, static, OSPF3.

D. ❌ – Includes IS-IS again, which is incorrect for CE-PE.

Question 25

Question 75: A CE is connected to an IES interface. Which of the following is TRUE? A. The IES's interface must be an IGP peer with the CE. B. The IES must use an IP address that is different than the CE. C. The IES can only include one SAP for the CE. D. The IES must include a network port.

Answer 25

B. The IES must use an IP address that is different than the CE. Answer Explanation: In Nokia's 7750 SR OS, an IES (Internet Enhanced Service) interface is a routed interface where each side of the point-to-point connection—CE and PE—requires a unique IP address for proper Layer 3 communication. This is fundamental to establishing IP routing protocols or static routing between the CE and PE. Option A is incorrect because IGP peering is optional; static routing is also valid. Option C is false—multiple SAPs can be supported depending on the service design. Option D is incorrect—an IES can use a variety of interfaces (e.g., access, not just network ports). Thus, Option B is correct.

Question 26

Question 76: Which of the following about VPRN route targets is FALSE? A. A route target is used to distinguish to which VRF table a prefix belongs. B. A route target appended to an IPv4 prefix produces a VPN-IPv4 prefix. C. Multiple route targets can be part of a single MP-BGP update. D. Route targets must be configured for VPRNs.

Answer 26

B. A route target appended to an IPv4 prefix produces a VPN-IPv4 prefix. Answer Explanation: This statement is false because the creation of a VPN-IPv4 prefix involves adding a route distinguisher (RD) to an IPv4 prefix — not a route target. Route targets are BGP extended community attributes used for route import/export control, determining which VRFs accept specific VPN-IPv4 routes. A is correct: Route targets determine VRF import/export behavior. C is correct: Multiple route targets can be carried in a single MP-BGP update. D is correct: VPRNs require route targets to control routing policy between sites. Thus, Option B is the false statement.

Question 27

Question 77: Which of the following about the components of a distributed service on the Nokia 7750 SR is TRUE? A. A SAP can only be used by one service on a router. B. A dedicated SDP needs to be created for each service. C. A service is created on each site before the customer is created. D. SAPs must be created before a service is created.

Answer 27

A. A SAP can only be used by one service on a router. Answer Explanation: In Nokia’s SR OS architecture, a Service Access Point (SAP) represents the local attachment point to a service. It is tied to a specific port and encapsulation. A given SAP can only be associated with one service instance. If you attempt to assign the same SAP to more than one service, the system will reject the configuration. This ensures clear separation of traffic and service policies. Evidence from the configuration in the CLI output: The SAP is created within the service configuration: sap 1/1/1:30 create Customer and service instances are created independently and then SAPs are assigned, respecting the rule that a SAP is unique per service.

Question 28

Question 78: Which of the following statements about the E-pipe service is TRUE? A. The service is a local service. B. The service requires a second spoke SDP on this router. C. The service's VC ID is 44. D. The service will accept VLAN tag 100.

Answer 28

C. The service's VC ID is 44. Answer Explanation: The Epipe configuration shown includes: epipe 12 customer 100 create ... spoke-sdp 2:44 create The "spoke-sdp 2:44" line indicates that the VC ID (Virtual Circuit Identifier) for the Epipe service is 44. This VC ID is used to identify the pseudowire associated with this specific Epipe instance across the SDP. A is incorrect: this is not a local service; it includes a remote SDP. B is incorrect: only one spoke SDP is configured. D is incorrect: no VLAN tag matching is specified or enforced in the config provided.

Question 29

Question 79: Which of the following about transport and service tunnels is FALSE? A. Service tunnels are unidirectional. B. Transport tunnels are unidirectional. C. A service will use the same service label for every hop. D. A local service requires a transport tunnel.

Answer 29

D. A local service requires a transport tunnel. Answer Explanation: Local services do not require a transport tunnel; they are confined to a single node (e.g., loopback connectivity, SAP-to-SAP on the same router). Service tunnels (like VLLs or VPLS over SDP) and transport tunnels (LSPs) are unidirectional — this is true. The same service label is used for all hops within a service path — this is also true. Therefore, the false statement is D, making it the correct choice for this question.

Question 30

Question 80: In a Layer 2 encapsulation using T-LDP, what does the second (bottom) label represent? A. Tunnel Label B. VC Label C. Operational Control Word D. VPI E. VCI

Answer 30

B. VC Label Answer Explanation: In Layer 2 VPN (L2VPN) services using T-LDP (Targeted Label Distribution Protocol), two MPLS labels are typically imposed: Outer (Top) Label: The transport or tunnel label, used to reach the remote PE (Provider Edge) router via an LSP (Label Switched Path). Inner (Bottom) Label: The VC (Virtual Circuit) Label, which identifies the specific pseudowire (or Epipe/VLL) instance on the remote PE. This VC Label is assigned by the remote PE during T-LDP signaling. VPI/VCI (D/E) are ATM terms and not used in MPLS VPNs. Operational Control Word (C) is an optional 4-byte field used for OAM or sequencing, not a label.

Question 31

Question 81: Which of the following statements about SAPs that are part of a VPVVS is FALSE? A. SAPs can be defined on Ethernet, POS, Sonet/SDH, or TDM channels. B. Only one SAP is required for a service that originates and terminates on the same Nokia 7750 SR. C. SAPs can have QoS policies assigned to them. D. Multiple SAPs can be defined on the same port.

Answer 31

B. Only one SAP is required for a service that originates and terminates on the same Nokia 7750 SR. Answer Explanation: This statement is false. VPVVS (Virtual Private Wire Service) requires two SAPs: one for ingress and one for egress, even if the service is local (originates and terminates on the same router). A single SAP is insufficient to complete the service instantiation. Clarifications: A is true: SAPs can exist on multiple physical media types. C is true: QoS policies can be applied at the SAP level. D is true: You can configure multiple SAPs on the same physical port using different VLANs or encapsulation criteria.

Question 32

Question 82: Which of the following about SAPs is TRUE? A. More than one SAP can be configured on a physical port that is configured for null encapsulation. B. Dot1Q Ethernet encapsulated access ports can support multiple SAPs and services. C. SAPs can be created on ports designated as "Network". D. SAPs can only be created on Ethernet ports.

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B. Dot1Q Ethernet encapsulated access ports can support multiple SAPs and services. Answer Explanation: B is TRUE: When a port uses 802.1Q encapsulation (dot1q), you can define multiple SAPs, each associated with a different VLAN ID, allowing multiple services to share the same physical port. Why others are FALSE: A is false: A null encapsulated port allows only a single SAP. C is false: SAPs cannot be configured on ports designated as "Network"—they are for service interfaces only. D is false: SAPs can also be configured on other types of ports like POS, SONET/SDH, TDM—not just Ethernet.

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Question 83: An E-pipe is configured with a service MTU of 5000. What is the minimum MTU value that should be set on an access port for a dot1q encapsulated SAP on this service? A. 5000 B. 5004 C. 5008 D. 5014

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B. 5004 Answer Explanation: When using dot1q encapsulation, an additional 4-byte VLAN header is added to the Ethernet frame. Therefore, the minimum physical port MTU must accommodate: The service MTU (5000 bytes) Plus the 4-byte dot1q VLAN tag Plus an additional 4 bytes for Ethernet overhead (often recommended for alignment and CRC) Thus: 5000 (service MTU) + 4 (dot1q tag) + 4 (Ethernet overhead) = 5008 bytes This ensures no fragmentation or dropped frames due to MTU mismatch at the access port.

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Question 84: Which of the following about VPLS MAC learning is FALSE? A. The PE routers of the service are responsible for learning MAC addresses. B. Flooding ensures that all PEs in a fully-meshed VPLS will learn the source address of all traffic. C. MAC learning reduces flooding of frames with previously learned addresses. D. Multiple VPLSes on the same PE share the same MAC FDB.

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D. Multiple VPLSes on the same PE share the same MAC FDB. Answer Explanation: Each Virtual Private LAN Service (VPLS) instance on a PE (Provider Edge) router maintains its own MAC Forwarding Database (FDB). This separation ensures traffic isolation between VPLS services. A is true – PE routers perform MAC learning. B is true – Flooding initially helps distribute MAC addresses. C is true – MAC learning reduces unnecessary flooding. D is false – Each VPLS has a unique MAC FDB; they are not shared across services.

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Question 85: By default, how does a VPLS handle a tagged frame received at the ingress of a null SAP on a Nokia 7750 SR? A. The FCS is verified and kept in the customer frame. The VLAN tag is kept and transported over the network. B. The FCS is verified and kept in the customer frame. The VLAN tag is removed for transport over the network. C. The FCS is verified and removed from the frame. The VLAN tag is kept and transported over the network. D. The FCS is verified and removed from the frame. The VLAN tag is removed for transport over the network.

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D. The FCS is verified and removed from the frame. The VLAN tag is removed for transport over the network. Answer Explanation: In a Nokia 7750 SR, when a frame enters a null SAP, by default: The FCS (Frame Check Sequence) is verified and removed. The VLAN tag is stripped off (not preserved) for null encapsulated SAPs, treating all traffic as untagged for transport. Thus, the frame is depacketized and carried over the MPLS/IP core without its original VLAN identifier unless otherwise configured.

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Question 86: This is output from router R4. Service 333 is a VPLS. Why does peer 10.10.10.1 not have an EgrLbl? A. The SDP to 10.10.10.1 on router R4 is shutdown. B. Router R4 has not sent a label to router R1 (10.10.10.1) yet. C. 10.10.10.1 has a different service MTU set. D. 10.10.10.1 has not sent a label to router R4 yet.

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D. 10.10.10.1 has not sent a label to router R4 yet. Explanation: For LDP FEC 128 (used in VPLS), bidirectional label bindings are needed. Since R4's EgrLbl for 10.10.10.1 is missing, it implies R1 (10.10.10.1) has not sent the outgoing label to R4. This is also confirmed by the RMTU being 0, showing no advertisement received.

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Question Number: 87 Question: How many service labels must be signaled to bring up a fully-meshed VPLS among three PE routers? A. 1 B. 3 C. 6 D. 12

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C. 6 Answer Explanation: In a fully meshed VPLS environment with three PE routers, each PE must form a bidirectional pair with the others using signaled service labels: PE1 ↔ PE2 PE1 ↔ PE3 PE2 ↔ PE3 Each direction requires a separate label. So, for 3 pairs × 2 directions = 6 labels total. Thus, the correct answer is 6.

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Question: 88 Which of the following is NOT a benefit of "Hub and Spoke" VPLS deployments? A. They reduce the number of SDPs that need to be configured. B. They can be used to work around physical topologies that prevent a fully meshed deployment. C. They prevent loops that can be introduced by mesh deployments. D. They can simplify the implementation of security policy enforcement and packet inspection.

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C. They prevent loops that can be introduced by mesh deployments. Answer Explanation: While hub-and-spoke VPLS can reduce complexity and number of SDPs, they do not inherently prevent loops. Loop prevention is generally handled by other mechanisms like split-horizon or MAC learning rules in VPLS, not the topology itself. Thus, C is NOT a valid benefit, making it the correct answer to this "NOT" question.

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Question: 89 Which utility on the Nokia 7750 SR can be used to investigate an MPLS path? A. Isp-trace B. Idp-trace C. Sdp-ping D. Svc-ping E. Ping

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A. Isp-trace Answer Explanation: The isp-trace command on a Nokia 7750 SR is used to trace the Label Switched Path (LSP) across an MPLS network. It performs a function similar to traceroute but is MPLS-aware, enabling engineers to identify each hop in the label-switched path and troubleshoot MPLS-specific issues such as label imposition, swapping, or termination. Other options: svc-ping: Used to test service connectivity (e.g., VPLS, VLL). sdp-ping: Tests connectivity over the Service Distribution Path. ping: Generic ICMP or LSP ping. idp-trace: Not a valid utility. Likely a distractor. Therefore, A. isp-trace is the correct tool to investigate MPLS paths. Test Number:

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Question 90 If the Nokia 7750 SR is rebooted after an "admin save" has been performed, which of the following about mirror services is TRUE? A. Only the mirror source must be re-configured. B. Only the mirror destination must be re-configured. C. Both the mirror destination and mirror source must be re-configured. D. Neither the mirror destination nor the mirror source must be re-configured.

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D. Neither the mirror destination nor the mirror source must be re-configured. Answer Explanation: On the Nokia 7750 SR, when using mirror services (used for port or service mirroring), configuration persistence is controlled by whether the settings have been saved. When you perform an admin save, all current configuration changes—including those related to mirror source and destination—are written to the boot configuration file. Upon reboot, the system reads from this saved configuration and automatically restores all services and settings, including mirroring. Thus, no manual reconfiguration is required after a reboot, as long as an admin save was done prior to reboot. Why Other Options Are Incorrect: A. Only the mirror source must be re-configured. ❌ Incorrect. The mirror source is saved and restored just like other config elements. B. Only the mirror destination must be re-configured. ❌ Incorrect. The mirror destination is also part of the saved config. C. Both the mirror destination and mirror source must be re-configured. ❌ Incorrect. This would be true only if you did not perform admin save before rebooting. ✅ D. Neither the mirror destination nor the mirror source must be re-configured. ✔ Correct. An admin save commits both source and destination mirror configs, preserving them across reboot.

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Question 91 This PE is connected to an IPv4 core and is being configured to support 6VPE for a VPRN. Which of the following completes this section of the configuration? A. Family ipv4 B. Family ipv6 C. Family ipv4 ipv6 D. Family vpn-ipv4 E. Family vpn-ipv4 vpn-ipv6

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E. Family vpn-ipv4 vpn-ipv6 Answer Explanation: In a 6VPE (IPv6 VPN over MPLS) scenario, the PE routers support both IPv4 and IPv6 VPN address families. Even though the core is IPv4-based, IPv6 customer routes are exchanged using MP-BGP over IPv4 transport, with IPv6 reachability encoded in VPNv6 (vpn-ipv6). Hence, to allow BGP to carry both IPv4 and IPv6 VPN prefixes, the BGP group must include: bash family vpn-ipv4 vpn-ipv6 This enables the correct AFI/SAFI for 6VPE deployments.

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Question 92 Part of a 6VPE deployment is shown. Which of the following is the correct configuration and context on router CE1 for a BGP peering session with 6VPE1? A. context ipv6 router bgp local-as 64497 neighbor 2001:db8:12::2 remote-as 64496 B. context ipv6-vpn router bgp local-as 64496 neighbor 2001:db8:12::1 remote-as 64497 C. context ipv6-vpn router bgp local-as 64497 neighbor 2001:db8:12::2 remote-as 64496 D. context ipv6 router bgp local-as 64497 neighbor 2001:db8:12::2 remote-as 64497

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A. context ipv6 router bgp local-as 64497 neighbor 2001:db8:12::2 remote-as 64496 Explanation: In a 6VPE deployment: CE1 is a customer edge router and does not support MPLS. The IPv6 BGP session is established between the CE and PE in the global IPv6 context, not the VPN context. On CE1: The context should be ipv6 CE1's AS is 64497 (local) PE1's AS is 64496 (remote) The correct peer IP is 2001:db8:12::2 (PE1 interface) Answer A matches all these conditions.

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Question 93 The output is from PE router R4 about VPRN service 100. How many prefixes have been learned from the MP-BGP protocol? A. 0 B. 2 C. 3 D. 6

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B. 2 Answer Explanation: From the output of the command (visible in the uploaded image), we see under the BGP table summary for service 100 on PE router R4 that the number of prefixes received via MP-BGP is 2. This indicates that two route entries have been learned via MP-BGP for this VPRN service. These routes are likely VPN-IPv4 routes with route distinguishers and VPN labels used for VPRN services. The output typically includes a line similar to: javascript Number of received prefixes: 2 Hence, the correct number of MP-BGP-learned prefixes is 2.

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Question 94 On a Nokia 7750 SR, what is the recommended approach for making sure that MTUs between a VPLS and its spoke IES termination match? A. Set the service MTU of the VPLS to match the IES MTU. B. Set the ip-mtu of the IES to match the service MTU of the VPLS. C. Set the SDP MTU of the IES to match the SDP MTU of the VPLS. D. Set the MTU of the IES's network port to match the service MTU of the VPLS. Correct Answer:B. Set the ip-mtu of the IES to match the service MTU of the VPLS.

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B. Set the ip-mtu of the IES to match the service MTU of the VPLS. Answer Explanation: In a Nokia 7750 SR configuration, when an IES service is terminated into a VPLS (such as in hub-and-spoke topologies), ensuring that the IP-MTU of the IES matches the service MTU of the VPLS is essential. This ensures proper forwarding and avoids fragmentation or dropped packets due to MTU mismatch. The IP MTU controls the largest packet size that can be processed without fragmentation at the IP layer, which should align with the service layer MTU of the VPLS for seamless L2/L3 integration. Let me know if you want this included in a printable or exportable format.

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Question 95 Which of the following about SAPs is FALSE? A. A SAP can be associated with more than one service. B. A SAP is the subscriber's point of entry to the service network. C. A SAP is created by specifying a physical port and an encapsulation type. D. A SAP can only be created on a port configured as "access".

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A. A SAP can be associated with more than one service. Answer Explanation: A SAP (Service Access Point) in Nokia 7750 SR OS is a unique attachment point between a service and a physical port. It cannot be associated with more than one service. Each SAP is uniquely defined by a physical port and encapsulation (e.g., 1/1/1:100) and is strictly bound to a single service (like VPLS, IES, or Epipe). Therefore, statement A is false, making it the correct answer to the Question.

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Question 96 In a Layer 2 encapsulation using T-LDP, what does the first (top) label represent? A. Tunnel Label B. VC Label C. Operational Control Word D. UNI E. NNI

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A. Tunnel Label Answer Explanation: In a Layer 2 VPN using T-LDP (Targeted Label Distribution Protocol) for signaling, two labels are typically used in the label stack: Top Label (outermost): This is the tunnel label used to reach the remote PE router (iLER → eLER). It is associated with the transport tunnel, such as LDP, RSVP-TE, or segment routing. Bottom Label: This is the VC (Virtual Circuit) label, which identifies the specific pseudowire (L2VPN service) within the transport tunnel. Thus, the first (top) label is the tunnel label, which ensures that the packet is transported across the MPLS core to the correct endpoint.

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Question 97 When configuring distributed services across a network, it is considered best practice to configure which of the following parameters as globally significant? A. Customer ID and SAP ID. B. Customer ID and Service ID. C. SAP ID and Service ID. D. SDP ID and Service ID. E. SDP ID and SAP ID. F. SDP ID and VC ID.

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B. Customer ID and Service ID. Answer Explanation: In a distributed service architecture (especially in service provider networks using Nokia 7750 SR), it's best practice to maintain global uniqueness for Customer IDs and Service IDs across the network. This ensures consistent service management, simplifies troubleshooting, and improves automation and provisioning processes. Customer ID: Identifies the customer globally. Service ID: Identifies the specific service instance across the network. This allows centralized provisioning tools and NMS systems to avoid overlapping configurations across PEs.

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Question 98 On a Nokia 7750 SR, which vc-type will strip service delimiting tags at the ingress PE? A. vc-type ether B. vc-type vlan C. vc-type dot1q D. vc-type null

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A. vc-type ether Answer Explanation: The vc-type ether option on Nokia 7750 SR is used in pseudowire (VPWS) configurations where no VLAN tag is preserved — this effectively strips the service delimiting tag (e.g., dot1q or q-in-q) at the ingress PE. The payload is treated as raw Ethernet and forwarded transparently. In contrast: vc-type vlan and vc-type dot1q would preserve VLAN information. vc-type null is used for local services or loopback testing and does not apply to label-based forwarding.

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Question 99 What happens by default on a Nokia 7750 SR when a null encapsulated SAP receives a frame with a VLAN tag? A. The original VLAN tag is removed. B. The original VLAN tag is kept. C. The VLAN tag is replaced by a provider tag. D. The VLAN tag is kept and a provider tag is added.

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A. The original VLAN tag is removed. Answer Explanation: On a Nokia 7750 SR, a null encapsulated SAP means there is no VLAN tag used to identify traffic at ingress. When such a SAP receives a frame with a VLAN tag, by default, the VLAN tag is stripped, and only the payload (Ethernet frame) is processed. This behavior aligns with the definition of a null encapsulated SAP, which expects untagged frames or treats incoming tags as insignificant.

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Question 100 Which of the following about ADSPEC is FALSE? A. ADSPEC sets an SDP’s MTU to the smallest MTU value found along the LSP path. B. RSVP must be enabled on all MPLS routers of a path to use ADSPEC. C. ADSPEC can automatically adjust the service MTU. D. ADSPEC can be enabled on individual LSPs.

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C. ADSPEC can automatically adjust the service MTU. Answer Explanation: ADSPEC (Advertisement Specification) is a feature used in RSVP-TE to dynamically determine the minimum MTU along the LSP path and apply it to the SDP. However, it does not automatically adjust the service MTU—that remains a manual configuration. The control of service MTU is separate and must be explicitly configured by the operator.