300-410 MPLS Operations Practice Test 2 — 15 Questions

Question 1

A network engineer runs the following command on Router R1:

R1# show ip nhrp
10.0.0.2/32 via 10.0.0.2, Tunnel0 created 00:15:30, expire 01:44:30
    Type: dynamic, Flags: used
    NBMA address: 192.168.1.2
10.0.0.3/32 via 10.0.0.3, Tunnel0 created 00:10:20, expire 01:49:40
    Type: dynamic, Flags: used
    NBMA address: 192.168.1.3

Based on this output, which statement is correct?

Accepted Answer

Both NHRP entries are active and dynamically learned.. The output shows two NHRP entries with 'Type: dynamic', meaning they were learned dynamically (not statically configured). Both have 'Flags: used', indicating they are active. The expiration times show they will expire in about 1 hour 44 minutes and 1 hour 49 minutes, respectively.

Answer

Both NHRP entries are static.

Answer

The NHRP entries have expired.

Answer

The NBMA addresses are IPv6 addresses.

Question 2

A network engineer runs the following command on Router R1:

R1# show policy-map control-plane

Control Plane

Service-policy input: CoPP

class-map: MANAGEMENT (match-all)
      5 packets, 500 bytes
      5 minute offered rate 0 bps
      police:
          cir 8000 bps, bc 1500 bytes
        conformed 5 packets, 500 bytes; actions:
          transmit
        exceeded 0 packets, 0 bytes; actions:
          drop
        conformed 0 bps, exceed 0 bps

class-map: ATTACK (match-all)
      100 packets, 10000 bytes
      5 minute offered rate 0 bps
      police:
          cir 8000 bps, bc 1500 bytes
        conformed 0 packets, 0 bytes; actions:
          transmit
        exceeded 100 packets, 10000 bytes; actions:
          drop
        conformed 0 bps, exceed 0 bps

Based on this output, what is happening to traffic matching class ATTACK?

Accepted Answer

All traffic in class ATTACK is being dropped.. The output shows that for class ATTACK, 100 packets were exceeded and dropped. This means the traffic rate exceeded the committed information rate (CIR) of 8000 bps, and all packets were dropped as per the exceed action.

Answer

All traffic in class ATTACK is being transmitted.

Answer

Traffic in class ATTACK is being rate-limited but not dropped.

Answer

Traffic in class ATTACK is being marked down.

Question 3

A network engineer runs the following command on Router R1:

R1# show ip sla statistics 1
IPSLAs Latest Operation Statistics
IPSLA operation id: 1
Type of operation: icmp-echo
Latest RTT: 10 milliseconds
Latest operation start time: 00:15:30 UTC Mon Mar 1 2021
Latest operation return code: OK
Number of successes: 100
Number of failures: 0
Operation time to live: Forever

Based on this output, which statement is correct?

Accepted Answer

The IP SLA operation is successful and has a low RTT.. The output shows an IP SLA operation of type icmp-echo with a return code 'OK', 100 successes, and 0 failures. This indicates the operation is functioning correctly.

Answer

The IP SLA operation has failed 100 times.

Answer

The IP SLA operation type is udp-jitter.

Answer

The IP SLA operation has expired.

Question 4

Examine the following partial MPLS configuration on a Cisco IOS-XE router:

interface GigabitEthernet0/0
 ip address 10.0.1.1 255.255.255.252
 mpls ip
 mpls label protocol ldp
!
router ospf 1
 network 10.0.1.0 0.0.0.3 area 0
!
mpls ldp router-id Loopback0 force

What is the effect of this configuration?

Accepted Answer

LDP will establish a session with the neighbor on GigabitEthernet0/0, using Loopback0 as the transport address.. The configuration enables LDP on the interface and globally via 'mpls ip'. The 'mpls label protocol ldp' is default but explicit. The 'mpls ldp router-id Loopback0 force' ensures LDP uses Loopback0 as the router ID, overriding any other interface. OSPF advertises the /30 link. This is a correct minimal MPLS configuration.

Answer

LDP will use the IP address of GigabitEthernet0/0 as the router ID because 'force' is not valid.

Answer

LDP sessions will fail because OSPF is not redistributed into LDP.

Answer

MPLS forwarding will not occur because 'mpls label protocol ldp' is redundant and causes a conflict.

Question 5

Consider the following MPLS configuration on a Cisco router:

ip cef
!
interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.252
 mpls ip
!
interface GigabitEthernet0/1
 ip address 192.168.2.1 255.255.255.252
 mpls ip
!
mpls ldp router-id GigabitEthernet0/0

What is the likely problem with this configuration?

Accepted Answer

The router-id command is incorrectly referencing a physical interface; LDP may flap if GigabitEthernet0/0 goes down.. The 'mpls ldp router-id' command expects a loopback interface or a stable IP address, not a physical interface name. Using a physical interface can cause LDP to flap if the interface goes down. Also, the command typically uses an interface's IP address, not the interface name directly. The correct syntax is 'mpls ldp router-id <interface> [force]', but it is best practice to use a loopback.

Answer

Missing 'mpls label protocol ldp' under the interfaces will prevent LDP from running.

Answer

Cisco Express Forwarding (CEF) must be explicitly enabled globally; it is not enabled by default.

Answer

The configuration is correct and will work without any issues.

Question 6

Given the following partial configuration:

ip cef
!
interface Loopback0
 ip address 10.0.0.1 255.255.255.255
!
interface GigabitEthernet0/0
 ip address 10.1.1.1 255.255.255.252
 mpls ip
!
router ospf 1
 network 10.0.0.1 0.0.0.0 area 0
 network 10.1.1.0 0.0.0.3 area 0
!
mpls ldp router-id Loopback0 force

What is missing from this configuration to ensure proper MPLS LDP operation?

Accepted Answer

Nothing is missing; the configuration is complete for basic MPLS LDP operation.. The configuration appears correct: CEF enabled, MPLS enabled on the interface, OSPF advertising all networks, and LDP router-id set to a loopback. There is no missing element for basic LDP operation. However, some might think 'mpls label protocol ldp' is needed, but it is default. The question tests if the candidate can identify that nothing is missing.

Answer

The 'mpls label protocol ldp' command is missing globally or on the interface.

Answer

The 'mpls ldp neighbor' command is needed to specify the neighbor's IP address.

Answer

The 'mpls ip' command must also be applied under the OSPF process.

Question 7

Examine this MPLS configuration on a router:

ip cef
!
interface GigabitEthernet0/0
 ip address 172.16.1.1 255.255.255.252
 mpls ip
!
interface GigabitEthernet0/1
 ip address 172.16.2.1 255.255.255.252
!
router eigrp 100
 network 172.16.0.0
!
mpls ldp router-id Loopback0 force

What is the problem with this configuration?

Accepted Answer

The 'mpls ldp router-id' command references Loopback0, but no loopback interface is configured, causing LDP to fail.. The LDP router-id is set to Loopback0, but Loopback0 is not configured. This will cause LDP to fail to establish a router ID, and LDP sessions will not form. Additionally, EIGRP is used but that is fine. The missing loopback interface is the key issue.

Answer

EIGRP is not supported with MPLS; OSPF or IS-IS must be used.

Answer

The 'mpls ip' command is missing on GigabitEthernet0/1, so MPLS will not work on that interface.

Answer

CEF must be enabled under each interface, not just globally.

Question 8

Consider the following configuration snippet:

ip cef
!
interface GigabitEthernet0/0
 ip address 10.0.0.1 255.255.255.252
 mpls ip
!
interface GigabitEthernet0/1
 ip address 10.0.1.1 255.255.255.252
 mpls ip
!
router ospf 1
 network 10.0.0.0 0.0.0.3 area 0
 network 10.0.1.0 0.0.0.3 area 0
!
mpls ldp router-id Loopback0 force
!
interface Loopback0
 ip address 192.168.0.1 255.255.255.255

What will happen when this router attempts to establish an LDP session with a neighbor on GigabitEthernet0/0?

Accepted Answer

LDP will use Loopback0 (192.168.0.1) as the transport address, but the neighbor must have a route to 192.168.0.1 for the session to establish.. The configuration is correct. LDP will use Loopback0 (192.168.0.1) as its router ID and transport address. The neighbor must be able to reach 192.168.0.1 via the IGP. Since OSPF advertises the loopback, it should work. The question tests understanding of LDP transport address usage.

Answer

LDP will use the IP address of GigabitEthernet0/0 as the transport address because Loopback0 is not in OSPF.

Answer

LDP will not use Loopback0 because the interface is not configured with 'mpls ip'.

Answer

LDP will use the IP address of GigabitEthernet0/1 because it has the highest IP among MPLS-enabled interfaces.

Question 9

Given the following configuration:

ip cef
!
interface GigabitEthernet0/0
 ip address 10.1.1.1 255.255.255.252
 mpls ip
!
interface GigabitEthernet0/1
 ip address 10.2.2.1 255.255.255.252
 mpls ip
!
router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
!
mpls ldp router-id Loopback0 force
!
interface Loopback0
 ip address 192.168.0.1 255.255.255.255

A network engineer notices that LDP sessions are not establishing. What is the most likely cause?

Accepted Answer

The LDP router ID is not reachable because the loopback is not advertised in OSPF.. The loopback is not advertised in OSPF because the network statement 10.0.0.0 0.255.255.255 does not include 192.168.0.1. The neighbor cannot reach the LDP router ID, so LDP sessions fail. This is a common oversight.

Answer

The OSPF network statement is too broad and causes routing issues.

Answer

The 'mpls ip' command is missing on Loopback0.

Answer

The 'force' keyword prevents LDP from using any other interface if Loopback0 is down.

Question 10

What is the default behavior of LDP when establishing a session between two directly connected routers?

Accepted Answer

LDP uses TCP port 646 for session establishment and UDP port 646 for hellos.. LDP uses hello messages to discover neighbors. By default, LDP hellos are sent to the multicast address 224.0.0.2 (all routers) on the local link. The session is established using the transport address, which by default is the router ID (usually the highest loopback or interface IP).

Answer

LDP sends hellos to the unicast address of each neighbor.

Answer

LDP hellos are sent to the all-OSPF-routers multicast address 224.0.0.5.

Answer

LDP sessions are established using UDP for reliability.

Question 11

In MPLS, what is the purpose of the TTL propagation feature?

Accepted Answer

It copies the IP TTL into the MPLS TTL at the ingress LER, allowing traceroute to see each hop in the MPLS path.. The TTL propagation feature controls how the IP TTL is handled when packets enter an MPLS domain. By default, the IP TTL is copied to the MPLS TTL (propagation), allowing traceroute to work across the MPLS network. When disabled, the MPLS TTL is set to 255, hiding the core from traceroute.

Answer

It propagates the MPLS label stack to all routers in the domain.

Answer

It prevents TTL from being decremented in the MPLS core for security purposes.

Answer

It ensures that the MPLS TTL is always equal to the IP TTL at the egress LER.

Question 12

Which of the following statements about MPLS label imposition and disposition is true?

Accepted Answer

The ingress LER performs the label push operation, and the egress LER performs the label pop operation unless PHP is used.. In MPLS, the ingress LER (Label Edge Router) imposes a label on the packet (push operation). The egress LER removes the label (pop operation). The penultimate hop router may perform penultimate hop popping (PHP) to remove the label before the egress, reducing the egress's workload.

Answer

The egress LER always performs the label pop operation.

Answer

The penultimate hop router always pushes an additional label.

Answer

Label disposition occurs only at the ingress LER.

Question 13

Which TWO commands would a network engineer use to verify the MPLS label forwarding table on a Cisco IOS-XE router? (Choose TWO.)

Accepted Answer

show mpls forwarding-table. The MPLS label forwarding table is verified using 'show mpls forwarding-table' and 'show mpls label table'. The former displays outgoing labels for prefixes, while the latter shows local label bindings. Other commands either show LDP neighbors or are invalid.

Answer

show mpls ldp neighbor

Answer

show ip route

Answer

show mpls interfaces

Question 14

Which TWO statements about MPLS label imposition (push) are true? (Choose TWO.)

Accepted Answer

Label imposition occurs at the ingress LSR.. Label imposition occurs at the ingress LSR, which pushes a label onto an unlabeled IP packet. The label is based on the FEC (Forwarding Equivalence Class) derived from the IP destination. The egress LSR pops the label, not imposes it.

Answer

Label imposition occurs at the egress LSR.

Answer

The imposed label is always the top label in a label stack.

Answer

Label imposition is performed using the 'tag-switching' command.

Question 15

Which THREE symptoms indicate a potential MPLS label switching issue on a Cisco router? (Choose THREE.)

Accepted Answer

The output of 'show mpls forwarding-table' shows 'no label' for a specific prefix.. MPLS issues often manifest as incorrect label operations. 'show mpls forwarding-table' showing 'no label' for a route indicates a missing label binding. 'show mpls ldp neighbor' showing 'state: OPERATIONAL' is normal, not a symptom. 'debug mpls ldp errors' showing 'Label bindings not received' indicates a problem. 'show mpls forwarding-table' showing 'Pop tag' for a non-egress router suggests a misconfiguration. 'show mpls interfaces' showing 'IP' only (not MPLS) indicates MPLS is not enabled on the interface.

Answer

The output of 'show mpls ldp neighbor' shows 'state: OPERATIONAL' for all neighbors.

Answer

The output of 'show mpls interfaces' shows 'IP' only for an interface configured for MPLS.