350-501 MPLS and Segment Routing — All Questions With Answers

An engineer is troubleshooting an MPLS L3VPN where customers behind CE1 cannot reach a specific prefix behind CE2. The PE routers are using OSPF as the IGP and LDP for label distribution. On PE2, the prefix is present in the VRF routing table, but not in the VRF forwarding table. What is the most likely cause?

Question 2hardmultiple choice

A service provider is designing a new MPLS core network using Segment Routing with MPLS data plane. They require traffic engineering capabilities to optimize bandwidth utilization. Which technology should be used to compute optimal paths based on IGP link attributes and bandwidth constraints?

Question 3easymultiple choice

An engineer is deploying MPLS in the core and wants to ensure that all core routers use the same label for a specific prefix, regardless of which router originated it. Which MPLS label allocation mode should be used?

Question 4mediummultiple choice

During an MPLS network migration from LDP to Segment Routing, an engineer notices that some routers are not advertising Prefix-SIDs for certain loopbacks. The IGP is OSPF. What configuration is required on these routers to advertise Prefix-SIDs?

Question 5hardmultiple choice

A service provider is deploying a new MPLS core with Segment Routing and requires fast convergence upon link failure. They plan to use TI-LFA (Topology Independent Loop-Free Alternate). What is a prerequisite for TI-LFA to provide protection against any single link failure?

Question 6mediummulti select

Which TWO statements about MPLS label switching are correct? (Choose two.)

Question 7hardmulti select

Which THREE of the following are benefits of using Segment Routing over LDP in an MPLS network? (Choose three.)

Question 8hardmultiple choice

Refer to the exhibit. A PE router in an MPLS L3VPN network shows the above output. The VRF CUSTOMER contains two routes. Which statement about forwarding for these routes is true?

Exhibit

Refer to the exhibit.

PE1# show mpls forwarding-table
Local  Outgoing    Prefix            Labels Label    Next Hop
16     Pop         10.1.1.0/24        
       No Label    10.2.2.0/24        

PE1# show ip bgp vpnv4 vrf CUSTOMER
Network          Next Hop      Metric LocPrf Weight Path
Route Distinguisher: 100:1
10.1.1.0/24      192.168.1.1          0    100      0 65001 i
10.2.2.0/24      192.168.2.2          0    100      0 65002 i

Question 9mediummultiple choice

Refer to the exhibit. An engineer configured Segment Routing on a router. However, the router does not advertise a Prefix-SID for the loopback0 interface. What is the most likely reason?

Exhibit

Refer to the exhibit.

interface GigabitEthernet0/0
 ip address 10.1.1.1 255.255.255.252
 mpls ip
 segment-routing mpls
!
router ospf 1
 segment-routing mpls
 prefix-sid index 100
 network 10.0.0.0 0.255.255.255 area 0
!
interface Loopback0
 ip address 192.168.1.1 255.255.255.255
 ip ospf 1 area 0
!

Question 10mediummultiple choice

A service provider is deploying MPLS L3VPN and notices that BGP next-hop resolution for VPNv4 routes fails on the PE routers. The PE routers are running OSPF as the IGP and have loopback interfaces used for LDP and BGP peering. Which configuration change should the engineer implement to ensure that the BGP next-hop is reachable?

Question 11easymultiple choice

An engineer is designing an MPLS network and needs to ensure that VPN traffic between two PE routers is label-switched. The PE routers are connected via a P router and have a full mesh of iBGP sessions. Which label distribution method is required for the VPN labels?

Question 12hardmulti select

A network engineer is troubleshooting an LDP session failure between two directly connected routers. The routers are configured with the 'mpls ldp' command under the interface. The 'show mpls ldp neighbor' command shows no neighbors. Which two additional pieces of information should the engineer verify? (Choose two.)

Question 13mediummultiple choice

Refer to the exhibit. A network engineer notices that the local label 19 for prefix 10.4.4.0/24 shows 'Untagged' in the outgoing label column. What is the most likely cause?

Exhibit

Refer to the exhibit.

PE1# show mpls forwarding-table
Local  Outgoing    Prefix           Bytes Label   Outgoing   Next Hop
Label  Label       or Tunnel Id     Switched      interface
16     Pop Label   10.1.1.0/24      0             Gi0/0/0    192.168.1.1
17     18          10.2.2.0/24      0             Gi0/0/1    192.168.2.2
18     19          10.3.3.0/24      0             Gi0/0/1    192.168.2.2
19     Untagged    10.4.4.0/24      0             Gi0/0/2    192.168.3.3

Question 14mediummulti select

Which TWO are benefits of using Segment Routing (SR) over traditional LDP-based MPLS?

Question 15hardmultiple choice

A service provider has a network with PE1, P1, P2, and PE2 connected in a chain: PE1-P1-P2-PE2. The IGP is IS-IS with wide metrics, and MPLS LDP is enabled on all interfaces. The goal is to provide L3VPN services between PE1 and PE2. The engineer has configured MP-iBGP between PE1 and PE2, and the VPNv4 routes are exchanged. However, when a CE router behind PE1 tries to reach the CE behind PE2, the traffic fails. The engineer checks the MPLS forwarding table on PE1 and sees that the label for the BGP next-hop (PE2's loopback) is 'Untagged'. The BGP next-hop is reachable via ICMP. What is the most likely cause of this issue?

Question 16easymultiple choice

A network operator is migrating from traditional MPLS LDP to Segment Routing (SR) with IS-IS. The network consists of four routers (R1-R4) in a square topology. The engineer has enabled SR on all routers and configured prefix-SIDs for loopbacks. However, when checking the MPLS forwarding table on R1, the engineer sees that some prefixes have label values that are not the prefix-SIDs. For example, the prefix for R4's loopback shows label 16004 instead of the expected 16004 (which is correct). But for another prefix, the label is 16003 instead of 16003 (correct). The engineer does not see any labels for some external routes. What is the most likely reason that some labels are missing?

Question 17mediummultiple choice

A service provider is deploying MPLS-TE with RSVP-TE in their core network. They notice that some LSPs are not being established due to resource contention. Which action would best address this issue without redesigning the entire traffic engineering deployment?

Question 18hardmultiple choice

Refer to the exhibit. An engineer is configuring Segment Routing for BGP (BGP-SR) on a PE router to assign labels to prefixes learned from a CE. The route-policy SET-LABEL is applied to the neighbor under the address-family ipv4 unicast. However, the CE prefix 10.1.1.0/24 is not receiving the label. What is the most likely reason?

Exhibit

Refer to the exhibit.

router bgp 65000
 neighbor 10.0.0.1 remote-as 65001
 neighbor 10.0.0.1 update-source Loopback0
 !
 address-family vpnv4
  neighbor 10.0.0.1 activate
  neighbor 10.0.0.1 send-community extended
 exit-address-family
!
route-policy SET-LABEL
  if destination in (10.1.1.0/24) then
    set label-index 100
  endif
 end-policy

Question 19easymultiple choice

A service provider is designing a greenfield MPLS core and wants to minimize control-plane complexity while still supporting traffic engineering. They plan to use Segment Routing with MPLS. Which statement about Segment Routing in this context is accurate?

Question 20mediumdrag order

Drag and drop the steps for the BGP route selection process (best path selection) in order.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 21mediumdrag order

Drag and drop the steps to configure a PPPoE client on a Cisco router into the correct order.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 22mediummatching

Match each IS-IS term to its definition.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Link State PDU containing routing information

Designated Intermediate System on a broadcast network

Network Service Access Point, the IS-IS address

Subnetwork Point of Attachment, e.g., MAC address

IS-IS Hello PDU used for neighbor discovery

Question 23mediummatching

Match each Ethernet OAM protocol to its function.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

Connectivity Fault Management for end-to-end Ethernet OAM

Performance monitoring including delay and loss measurement

Ethernet in the First Mile OAM for link-level monitoring

Link Aggregation Control Protocol for bundling links

Link Layer Discovery Protocol for neighbor discovery

Question 24mediummultiple choice

A service provider is implementing MPLS in their core network. They want to ensure that labeled packets for BGP prefixes are forwarded correctly without requiring an IGP label for every BGP prefix. Which technique should be used to achieve this?

Question 25hardmultiple choice

An engineer is troubleshooting an MPLS VPN issue where CE1 cannot ping CE2 across the provider network. The PE routers are configured with MP-BGP and LDP. On PE1, 'show ip bgp vpnv4 vrf CUST' shows the route to CE2's loopback as valid, but 'show mpls forwarding-table' does not list a label for that prefix. What is the most likely cause?

Question 26easymultiple choice

A network engineer is designing an MPLS core using Segment Routing. They want to minimize label stack depth while still providing fast convergence using TI-LFA. Which prefix-SID assignment strategy should be used?

Question 27mediummultiple choice

Refer to the exhibit. An engineer notices that R1 has an LDP neighbor but 'show mpls forwarding-table' on R1 shows no label bindings for prefixes learned from R2. What is the most likely cause?

Exhibit

R1# show mpls ldp neighbor
    Peer LDP Ident: 10.0.0.2:0; Local LDP Ident: 10.0.0.1:0
	TCP connection: 10.0.0.2.646 - 10.0.0.1.54658
	State: Oper; Msgs sent/rcvd: 100/100; Downstream on demand
	Up time: 01:23:45
	LDP discovery sources:
	  GigabitEthernet0/0/0; hello interval: 5 s, hold time: 15 s
	Addresses bound to peer LDP Ident:
	  10.0.0.2    10.1.1.2

Question 28hardmultiple choice

A service provider is migrating from LDP to Segment Routing in an IS-IS network. After enabling IS-IS with segment-routing on all routers, they observe that some prefixes still receive labels from LDP instead of from SR. Which configuration is most likely missing on these routers?

Question 29easymultiple choice

An engineer is configuring an MPLS Traffic Engineering tunnel using RSVP-TE. The tunnel is intended to carry voice traffic with strict delay requirements. Which RSVP-TE object should be used to enforce a maximum delay path?

Question 30hardmultiple choice

A network operator is deploying Segment Routing with TI-LFA across an OSPF network. After configuring OSPF with 'segment-routing mpls' and 'fast-reroute per-prefix', they notice that backup paths are not being installed for some prefixes. 'Show ip ospf segment-routing protected' shows 'No FRR backup' for those prefixes. What is a possible reason?

Question 31mediummultiple choice

A large enterprise uses MPLS L3VPN to connect multiple sites. They want to implement inter-AS option B (ASBR-to-ASBR MP-eBGP) for scalability. Which statement about this model is correct?

Question 32easymultiple choice

An MPLS core network uses LDP to distribute labels. An engineer wants to verify that the LDP session between two routers is up and exchanging labels. Which command should be used?

Question 33mediummulti select

Which TWO statements correctly describe Segment Routing characteristics? (Select two.)

Question 34hardmulti select

Which THREE are valid methods to provide fast convergence in an MPLS/Segment Routing network? (Select three.)

Question 35easymulti select

Which TWO types of SIDs are defined in Segment Routing? (Select two.)

Question 36mediummultiple choice

Refer to the exhibit. An engineer is troubleshooting packet loss in the MPLS core. For prefix 10.3.3.0/24, the outgoing label is 'Untagged'. What does this indicate?

Exhibit

PE1# show mpls forwarding-table
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id    Switched      interface              
16         Pop       10.1.1.0/24     0             Gi0/0/0    10.0.0.2    
17         19         10.2.2.0/24     1234          Gi0/0/0    10.0.0.2    
18         Untagged   10.3.3.0/24     0             Gi0/0/0    10.0.0.2

Question 37hardmultiple choice

Refer to the exhibit. An operator configures an SR-TE policy on a headend router. Which statement is true about the traffic steered into this policy?

Exhibit

segment-routing traffic-engineering
 policy POLICY1
  color 100 end-point 192.0.2.1
  candidate-path path1
   preference 50
   explicit segment-list SEG1
!
 segment-list SEG1
  index 10 mpls label 16000
  index 20 mpls label 16001
  index 30 mpls label 16002
!

Question 38hardmultiple choice

A service provider is troubleshooting an MPLS L3VPN issue where a CE router is receiving the VPN route from the PE but cannot ping the remote CE's loopback. The PE shows that the VPN label is assigned but cannot route the packets. Which command would help determine if the remote PE is correctly resolving the BGP next-hop via IGP?

Question 39easymultiple choice

Which protocol is typically used to distribute MPLS labels between directly connected LSRs?

Question 40mediummultiple choice

Which BGP address family must be used to exchange VPNv4 routes between PE routers in an MPLS L3VPN?

Question 41hardmultiple choice

An engineer is troubleshooting MPLS traffic engineering tunnels and needs to verify path calculation and RSVP errors. Which command should be used?

Question 42easymultiple choice

In MPLS forwarding, what label operation does a transit LSR perform on the top label of a labeled packet?

Question 43mediummultiple choice

Which BGP extended community is used to signal the OSPF domain ID between PE routers in an MPLS L3VPN when OSPF is the PE-CE protocol?

Question 44hardmultiple choice

A service provider wants to use Segment Routing TE with Flex-Algo to engineer traffic around links with low bandwidth. Which configuration approach should be taken?

Question 45easymultiple choice

Which tool can verify connectivity along an MPLS Label Switched Path (LSP) and detect label loops?

Question 46easymultiple choice

An engineer notices that MPLS VPN traffic is taking a suboptimal path because the MPLS label binding for the BGP next-hop loopback is missing. What is the most likely cause?

Question 47hardmultiple choice

In an MPLS L3VPN network with route reflectors, what is the default behavior regarding the BGP next-hop attribute for reflected VPNv4 routes?

Question 48mediummulti select

Which two statements about MPLS label distribution are correct? (Choose two)

Question 49hardmulti select

Which three features are unique to Segment Routing when compared to traditional MPLS with LDP? (Choose three)

Question 50easymulti select

Which two MPLS OAM tools can be used to troubleshoot label switching paths? (Choose two)

Question 51mediummultiple choice

Based on the exhibit, which prefix is missing a label binding and likely causing traffic to be dropped?

Exhibit

Refer to the exhibit. The output below is from a Cisco router.

R1# show mpls forwarding-table
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label     or Tunnel Id     Switched      interface              
16         27        10.1.1.0/24      0             Gi0/0      172.16.1.2
17         31        10.2.2.0/24      0             Gi0/0      172.16.1.2
18         Pop Label 10.3.3.0/24      0             Gi0/1      172.16.2.2
19         No Label  10.4.4.0/24      no vif        Gi0/2      172.16.3.2
20         35        10.5.5.0/24      0             Gi0/0      172.16.1.2

Question 52mediummultiple choice

The CE router behind the VRF interface is unable to reach the remote CE. Which configuration error is most likely the cause?

Exhibit

Refer to the exhibit. The configuration snippet is from a PE router in an MPLS L3VPN setup.

ip vrf CUSTOMER
 rd 100:1
 route-target export 100:1
 route-target import 100:1
!
interface GigabitEthernet0/0
 ip vrf forwarding CUSTOMER
 ip address 192.168.1.1 255.255.255.252
!
interface GigabitEthernet0/1
 ip address 10.0.0.1 255.255.255.252
 mpls ip
!
router bgp 100
 bgp log-neighbor-changes
 neighbor 10.0.0.2 remote-as 100
 neighbor 10.0.0.2 update-source Loopback0
 !
 address-family vpnv4
  neighbor 10.0.0.2 activate
  neighbor 10.0.0.2 send-community extended
 !
 address-family ipv4 vrf CUSTOMER
  redistribute connected
 !

Question 53hardmultiple choice

What does the output indicate about the TI-LFA protection on R1?

Exhibit

Refer to the exhibit. The output is from a Cisco router after configuring Segment Routing with TI-LFA.

R1# show isis fast-reroute summary
Number of prefixes with backup paths: 1
TI-LFA:
  Primary Protection: Enabled
  Node Protection: Enabled
  SRLG Protection: Disabled

Question 54easymultiple choice

A service provider is deploying MPLS in their core network and wants to ensure that all routers in the MPLS domain can dynamically exchange label bindings. Which protocol should be enabled on all routers to meet this requirement?

Question 55easymultiple choice

A network engineer is configuring Segment Routing on an IOS-XR router. They want to use the preferred algorithm for automatically computing paths based on IGP metrics. Which algorithm should be configured under the SR segment list?

Question 56easymultiple choice

During MPLS LDP operation, a router receives a label mapping for a prefix from its neighbor. What is the correct behavior when the receiving router has a route to that prefix?

Question 57mediummultiple choice

An engineer is troubleshooting MPLS label switching in a service provider core. They notice that packets are being forwarded correctly between provider edge routers, but when they check the MPLS forwarding table on a P router, they see only implicit-null labels for some destinations. What is the most likely reason for this?

Question 58mediummultiple choice

A service provider is using Segment Routing with TI-LFA for fast convergence. During a link failure, the router performing the local repair must compute a backup path that avoids the failed link. Which type of Adjacency Segment Identifier (Adj-SID) is required for the backup path to be loop-free?

Question 59mediummultiple choice

A network operator is configuring RSVP-TE tunnels for traffic engineering in an MPLS core. They want to enforce that the tunnel path strictly follows a predefined set of hops. Which explicit path option should be used?

Question 60hardmultiple choice

In an MPLS L3VPN network, a customer has overlapping IP addresses between two VPNs. The provider edge routers are configured with VRF instances. Which method ensures that traffic from one VPN does not leak into the other when using MPLS labels?

Question 61hardmultiple choice

A service provider is implementing Segment Routing over IPv6 (SRv6) in their core. They want to provide path isolation for different services using SRv6 SIDs. Which SID structure is used to encode both the locator and the function?

Question 62hardmultiple choice

An MPLS network is experiencing micro-loops during convergence after a link failure. The network uses LDP and IS-IS as IGP. Which of the following solutions can prevent micro-loops during IGP convergence without requiring additional protocols?

Question 63easymulti select

Which two statements about MPLS label operations are true? (Choose two.)

Question 64mediummulti select

Which three are required components for deploying Segment Routing in an MPLS network? (Choose three.)

Question 65hardmulti select

Which two are characteristics of the Anycast SID in Segment Routing? (Choose two.)

Question 66easymultiple choice

Refer to the exhibit. The show command output displays the LDP neighbor state. What does the 'Downstream' label mode indicate about label distribution?

Exhibit

Refer to the exhibit.

Router# show mpls ldp neighbor
Peer LDP Ident: 192.168.1.2:0; Local LDP Ident: 192.168.1.1:0
TCP connection: 192.168.1.2.646 - 192.168.1.1.58370
State: Operacional; Msgs sent/rcvd: 342/341; Downstream
Up time: 02:34:21
LDP discovery sources:
  GigabitEthernet0/0/0/0; Src IP addr: 192.168.1.2, transport address: 192.168.1.2
  targeted-hello 192.168.1.2 -> 192.168.1.1
  holdtime: 15 sec; proposed local/peer: 15/15
  LDP id: 192.168.1.2:0

Question 67mediummultiple choice

Refer to the exhibit. A network engineer is configuring a segment routing traffic engineering policy. The output shows two candidate paths. Why is path1 selected as the active path even though path2 has a bandwidth constraint?

Exhibit

Refer to the exhibit.

Router# show segment-routing traffic-eng policy
Policy name: TE_POLICY_1
  Color: 10
  Endpoint: 192.168.100.1
  Candidate-path name: path1
    Preference: 200
    Path type: explicit, verification source: local
    Explicit segment-list: SL_1
      Segment-list: SL_1
        Index: 1, Label: 16001
        Index: 2, Label: 16005
        Index: 3, Label: 16009
    Candidate-path name: path2
      Preference: 100
      Path type: dynamic, metric: TE
      Constraints: bandwidth 10000 kbps
        Affinity: include-any GREEN
  Status: Active path: path1 (preference 200)
  Forwarding status: Up

Question 68hardmultiple choice

Refer to the exhibit. The output shows an MPLS forwarding entry with FRR protection. What is the purpose of the backup path shown?

Exhibit

Refer to the exhibit.

Router# show mpls forwarding-table 192.168.10.0/24 detail
Local  Outgoing    Prefix            Bytes Label   Outgoing   Next Hop
Label  Label       or Tunnel Id      Switched      interface
200    16015       192.168.10.0/24   1000          Gi0/0/0    10.1.1.2
      MAC/Encaps: 14/18, MTU: 1500, Label Stack {16015(vcd)}
      VPN label: 1234 (L3VPN)
      Paths: 1 active
      Backup path: via Gi0/0/1, 10.1.1.6, label 16020
      Protection: FRR active, state: ready
      Time since last switch: 00:01:23

Question 69easymultiple choice

A service provider is designing a new MPLS core network and wants to simplify traffic engineering without deploying a centralized controller. Which technology should be used to enable source-routed paths with explicit path control?

Question 70mediummultiple choice

A network engineer is troubleshooting MPLS L3VPN issues on a PE router. The CE router is receiving routes from the PE, but the CE cannot ping the remote CE. The PE shows the remote prefix in its routing table and in the VRF. What is the most likely cause?

Question 71hardmultiple choice

A service provider is migrating from LDP-based MPLS to Segment Routing (SR-MPLS) with IS-IS. After enabling SR on all routers, the adjacency segment IDs (ADJ-SIDs) are not being advertised. Which configuration is missing?

Question 72easymultiple choice

A network architect is designing an MPLS network that must provide fast convergence in case of a link failure. The network uses Segment Routing. Which mechanism provides sub-50ms protection by using a precomputed backup path?

Question 73mediummultiple choice

A service provider is deploying MPLS L2VPN using Virtual Private Wire Service (VPWS). After configuration, the two CEs cannot ping each other. The PE routers show the xconnect interface is up, but no MAC addresses are learned. What is the most likely cause?

Question 74hardmultiple choice

A network engineer notices that BGP-LU prefixes learned from an eBGP neighbor are not being installed in the MPLS forwarding table (LFIB). The BGP table shows the prefixes with the correct label. The IGP route to the neighbor is reachable. What additional configuration is needed?

Question 75mediummultiple choice

A company is connecting two sites using MPLS L3VPN. The PE routers are running both LDP and Segment Routing (SR-MPLS) in the core. The CE router at Site A cannot reach the CE at Site B. On the PEs, the VRF routes are present. Which command would you use to verify the MPLS forwarding path for the VPN traffic?

Question 76easymulti select

Which TWO are characteristics of Segment Routing (SR-MPLS)? (Choose two.)

Question 77mediummulti select

Which THREE steps are required when configuring MPLS L3VPN on a PE router? (Choose three.)

Question 78hardmulti select

Which TWO commands are most effective to verify that an SR-TE policy is active and forwarding traffic? (Choose two.)

Question 79hardmultiple choice

A large service provider runs a dual-stack MPLS core with Segment Routing (SR-MPLS) and IS-IS as the IGP. The network has been operating stably for months. Recently, a new PE router (PE-5) was added and configured with IS-IS and SR. After the addition, some remote prefixes in the VRF on other PEs become unreachable. Troubleshooting reveals that the BGP next hop for those prefixes is the loopback of another PE (PE-3), but the MPLS forwarding table on PE-3 shows no label for the prefix. The IS-IS database on PE-3 shows the prefix-SID for PE-5's loopback, but the forwarding table does not have a label for that prefix. Commands like 'show mpls forwarding-table' show no entry for PE-5's loopback. What is the most likely cause and correct action?

Question 80mediummultiple choice

A service provider is troubleshooting an MPLS L3VPN scenario where a customer in VRF Blue cannot reach a server in VRF Blue at a remote site. The PEs are running MPLS with LDP. The VRF on both PEs shows the remote prefix. The PE at the local site shows the label from the remote PE for the prefix in the BGP table. However, when pinging from the CE, the packets are dropped. A packet capture on the core shows MPLS packets with the correct VPN label, but the transport label is missing. Further investigation shows that the LDP session between the two PEs is up, but the LDP label binding for the remote PE's loopback is not present. What is the most likely cause and correct action?

Question 81hardmultiple choice

A service provider has deployed Segment Routing (SR-MPLS) with OSPF as the IGP. They enabled TI-LFA for link protection. During a maintenance window, they shut down a core link between two P routers. Expected behavior is that TI-LFA should provide sub-50ms failover. However, after the shutdown, traffic loss exceeds 10 seconds. Analysis shows that the backup path uses a segment list that includes a node SID from a router that is currently unreachable due to the same failure. The TI-LFA backup path calculation appears to have included a node that is dependent on the failed link. What design issue is most likely causing this?

Question 82easymultiple choice

A service provider is migrating from a legacy MPLS network using LDP to Segment Routing (SR-MPLS). They have enabled SR on all routers and are using IS-IS. The migration plan is to keep LDP running alongside SR during the transition. After enabling SR, some traffic is being forwarded using the SR path, but the network operator notices that some CEs in an L2VPN are experiencing packet loss during failover scenarios. Troubleshooting shows that the primary pseudowire is using SR labels, but the backup pseudowire is still using LDP labels. The backup path is not working correctly. What is the most likely cause?

Question 83mediummultiple choice

A network engineer is configuring an MPLS L3VPN on a PE router. The VRF is configured with route-target import/export. The PE and CE are running eBGP. The CE advertises routes to the PE, and the PE installs them in the VRF routing table. However, the remote PE does not receive these routes via BGP VPNv4. The local PE's BGP table shows the VPNv4 prefixes with the correct next hop and label. The remote PE's BGP table shows no such prefixes. The IGP between the PEs is working, and MPLS LSPs are up. What is the most likely cause and correct action?

Question 84mediummultiple choice

A service provider is migrating their MPLS core network to Segment Routing (SR-MPLS). All existing core routers run IOS-XR and are configured with an SRGB of 16000-23999 and OSPF as the IGP. A new router (R5) is added as a PE. The engineer configures R5 with the same SRGB and enables segment-routing under OSPF. However, when configuring an SR-TE policy from R5 to the remote loopback 10.0.0.1 on R1, the policy remains down. Show commands reveal that R5 is not learning the prefix-SID for 10.0.0.1. On R1, the prefix-SID is configured with index 100. The engineer verifies that OSPF adjacencies are up and that R5 can ping 10.0.0.1. What is the most likely cause of the issue?

Question 85mediummultiple choice

A service provider is migrating from LDP to Segment Routing in its MPLS core. The team has enabled IS-IS as the IGP and configured segment routing under the IS-IS process on all core routers. However, after the migration, some LSPs are not being signaled correctly and traffic is blackholing. Which action should be taken to ensure seamless interworking between LDP and SR during the migration?

Question 86easymultiple choice

An SP network engineer is designing a new segment routing traffic engineering deployment within a single IGP area. The network consists of 50 core routers running IS-IS and MPLS. The engineer needs to steer traffic from Router A to Router D over a path that avoids high latency links. Which technology should be used to define and instantiate the explicit path?

Question 87hardmulti select

In an MPLS L3VPN network, a route reflector (RR) is used to distribute VPNv4 routes between PE routers. After a new PE router (PE4) is added, some VPN routes are not being received by other PEs. Which TWO actions should be investigated to resolve the issue? (Choose two.)

Question 88mediummultiple choice

Refer to the exhibit. The router has three LDP neighbors established. A network administrator notices that MPLS labels for the prefix 10.4.4.0/24 are not being advertised from this router to its neighbors, although the prefix is present in the routing table. Which is the most likely cause?

Exhibit

Router# show mpls ldp neighbor
Peer LDP Ident: 10.1.1.2:0; Local LDP Ident: 10.1.1.1:0
        TCP connection: 10.1.1.2.646 - 10.1.1.1.35399
        State: Oper; Msgs sent/rcvd: 148/143; Downstream
        Up time: 02:15:10
        LDP discovery sources:
          GigabitEthernet0/0/0; Src IP addr: 10.1.1.2
        Addresses bound to peer LDP Ident:
          10.1.1.2        10.2.2.2
        Peer LDP Ident: 10.2.2.2:0; Local LDP Ident: 10.1.1.1:0
        TCP connection: 10.2.2.2.646 - 10.1.1.1.49201
        State: Oper; Msgs sent/rcvd: 73/67; Downstream
        Up time: 01:10:45
        LDP discovery sources:
          GigabitEthernet0/0/1; Src IP addr: 10.2.2.2
        Addresses bound to peer LDP Ident:
          10.2.2.2        10.3.3.3
        Peer LDP Ident: 10.3.3.3:0; Local LDP Ident: 10.1.1.1:0
        TCP connection: 10.3.3.3.646 - 10.1.1.1.52001
        State: Oper; Msgs sent/rcvd: 53/49; Downstream
        Up time: 00:45:30
        LDP discovery sources:
          GigabitEthernet0/0/2; Src IP addr: 10.3.3.3
        Addresses bound to peer LDP Ident:
          10.3.3.3        10.4.4.4

Question 89easymultiple choice