300-410 Practice Test 38 — 15 Questions

Question 1

A network engineer configures SNMPv3 with authentication and privacy on a router. The NMS polls the router via the management interface. The engineer then adds a loopback interface and configures the router to send SNMP traps sourced from the loopback IP. The NMS stops receiving traps. Which is the most likely explanation?

Accepted Answer

The NMS is configured to accept traps only from the management interface IP address, not the loopback IP.. When traps are sourced from a different IP address, the NMS may not recognize the sender if it expects traps from the original IP. Additionally, if the loopback IP is not reachable from the NMS, traps are lost.

Answer

The loopback interface does not support SNMP trap generation.

Answer

The SNMP engine ID changed when the loopback interface was added.

Answer

The 'snmp-server trap-source' command requires a specific interface type.

Question 2

A BGP-speaking router R1 is redistributing BGP routes into EIGRP. R1 has configuration: router bgp 100 redistribute eigrp 100. Router R2, an EIGRP neighbor, shows: 'show ip route eigrp' includes some BGP routes but with high metrics. Traffic to those destinations is suboptimal. What is the root cause?

Accepted Answer

R1 has a route-map that sets the metric to 100000 1000 255 1 1500, which is too high, causing suboptimal path selection.. When redistributing BGP into EIGRP, the metric must be set explicitly; otherwise, EIGRP uses default metric values (if configured) or rejects the routes. If the metric is set via a route-map or default-metric, incorrect values can cause high metrics.

Answer

R1 has no default-metric configured for EIGRP, so redistributed BGP routes use the default metric of infinity, causing them to be unreachable.

Answer

BGP routes have a lower administrative distance than EIGRP, so they are not installed.

Answer

R2 has a route filter that increases the metric for BGP-originated routes.

Question 3

An engineer configures SNMPv2c with a community string 'public' and an ACL that permits the NMS. The NMS can poll the router. The engineer then applies a CoPP policy that drops SNMP packets (UDP port 161) from all sources except the NMS. The NMS now fails to poll. Which is the most likely explanation?

Accepted Answer

The CoPP policy's ACL does not include the NMS IP address, so SNMP packets from the NMS are dropped by the class-default.. CoPP applies to control plane traffic. If the CoPP policy is misconfigured, it may drop SNMP packets even from permitted sources. Additionally, the ACL in the CoPP policy must match the source IP of the NMS; if the ACL is incorrect or if the CoPP class-default drops all traffic, polling fails.

Answer

CoPP only affects routing protocol traffic, not SNMP.

Answer

The SNMP community string ACL is overridden by the CoPP policy.

Answer

The router requires a reload for the CoPP policy to take effect.

Question 4

An OSPF network has a multi-access link between routers R1 and R2. R1 is configured with 'ip ospf network point-to-point' on the interface, while R2 uses the default broadcast network type. R1 shows: 'show ip ospf neighbor' lists R2 as FULL/DR, but R2 shows: 'show ip ospf neighbor' lists R1 as FULL/DROTHER. Traffic from R1 to R2's loopback is fine, but from R2 to R1's loopback is intermittent. What is the root cause?

Accepted Answer

R1's point-to-point configuration disables DR/BDR election, but R2 still expects it, causing R1 to ignore R2's LSUs.. Network type mismatch causes OSPF to behave differently on each side. R1 sees the link as point-to-point, so it does not participate in DR/BDR election. R2 sees it as broadcast, so it elects a DR (itself). This can cause adjacency issues and suboptimal forwarding because R1 may not have the correct next-hop information.

Answer

R2's DR election is incorrect because it has a higher router ID, but R1 should be the DR.

Answer

R1's interface has an MTU mismatch that causes OSPF packets to be dropped.

Answer

R2 has a firewall that blocks OSPF packets from R1.

Question 5

A network engineer configures SNMPv3 with authentication and privacy on a router. The NMS polls the router successfully. The engineer then configures IPsec to encrypt all traffic between the router and the NMS. The NMS now fails to poll the router. Which is the most likely explanation?

Accepted Answer

The IPsec configuration does not include an ACL that matches SNMP traffic (UDP port 161).. IPsec encryption of SNMP traffic can cause issues if the IPsec configuration does not match the SNMP traffic or if the IPsec security association (SA) is not established. Additionally, SNMPv3 already provides encryption; double encryption may cause performance issues or misconfiguration.

Answer

SNMPv3 encryption and IPsec encryption are incompatible and cannot be used together.

Answer

The IPsec configuration uses aggressive mode, which is incompatible with SNMPv3.

Answer

The router's SNMP process must be restarted after IPsec is configured.

Question 6

An EIGRP network is experiencing frequent stuck-in-active (SIA) events. Router R1 shows: 'show ip eigrp topology' includes routes in active state for several minutes. R1's configuration: router eigrp 100 timers active-time 3. R2, a neighbor, is reachable but has a large number of routes. What is the root cause?

Accepted Answer

The active-time timer is set too low (3 minutes), causing queries to time out before R2 can reply.. The active-time timer is set to 3 minutes, which is the default. If a query is sent to a neighbor that takes longer than 3 minutes to reply (due to large topology or slow convergence), the route goes SIA. Reducing the active-time timer can cause premature SIA events.

Answer

R2 has a stuck-in-active condition due to a routing loop.

Answer

R1 has a misconfigured distribute-list that blocks query replies from R2.

Answer

The network has a high latency link that delays query propagation.

Question 7

A DMVPN network with EIGRP as the routing protocol is experiencing spoke-to-spoke tunnel failures. Spoke routers R1 and R2 are both connected to hub R3. R1 shows: 'show ip nhrp' lists R2's NBMA address, but 'show ip eigrp neighbors' does not show R2. R1's configuration: interface Tunnel0 ip nhrp network-id 1 ip nhrp nhs 10.0.0.3. What is the root cause?

Accepted Answer

R1 has no EIGRP configuration on the tunnel interface, so it does not send hellos over the tunnel.. In DMVPN, spoke-to-spoke tunnels require NHRP to resolve the NBMA addresses. If EIGRP is not configured to use the tunnel interface for neighbor discovery, or if the EIGRP hello packets are not being sent over the tunnel, the neighbor relationship fails.

Answer

R2's NHRP registration is incomplete, so R1 cannot reach R2's NBMA address.

Answer

The hub R3 is not configured to forward EIGRP packets between spokes.

Answer

R1's tunnel interface has an ACL that blocks EIGRP packets.

Question 8

An MPLS network with EIGRP as the IGP is experiencing label distribution failures. Router R1 shows: 'show mpls ldp neighbor' does not list R2. R1's configuration: mpls ip on interfaces, but no router-id configured. R2's configuration: mpls ldp router-id Loopback0 force. R1 and R2 are directly connected. What is the root cause?

Accepted Answer

R1's LDP router-id is not configured, so it uses the IP of the interface facing R2, which may not be reachable from R2's loopback.. LDP uses a router-id to establish sessions. If R1 does not have a router-id configured, it may use an interface IP that is not reachable from R2, causing the LDP session to fail.

Answer

R2 has a loopback interface that is not advertised via EIGRP, so R1 cannot reach it.

Answer

R1 has an ACL that blocks LDP UDP packets (port 646).

Answer

R2's 'force' keyword causes it to use the loopback even if it is not reachable.

Question 9

A network engineer notices that the syslog server at 10.1.1.100 is not receiving any log messages from a Cisco router running IOS-XE 16.9. The engineer has configured 'logging host 10.1.1.100' and 'logging trap debugging'. The router can ping the syslog server successfully. What is the most likely cause of the missing syslog messages?

Accepted Answer

The 'logging on' command is not configured globally.. The 'logging trap debugging' command sets the severity level to 7 (debugging), but the default logging source interface is the lowest-numbered IP address on the router. If that interface is not reachable from the syslog server, messages may be dropped. However, the more common issue is that the 'logging on' command is missing, which globally disables syslog output. Without 'logging on', no messages are sent to any syslog server regardless of other configurations.

Answer

The syslog server is using UDP port 514, but the router is sending over TCP.

Answer

The 'logging source-interface' is set to a loopback that is not advertised in the routing table.

Answer

The 'logging buffered' command is overriding the remote logging configuration.

Question 10

A network uses ACLs to filter traffic. Router R1 has the following ACL applied to interface GigabitEthernet0/0 in the inbound direction: access-list 100 permit tcp any any eq 22. Router R2, connected to R1, cannot SSH to R1's loopback address. R1 shows: 'show ip interface GigabitEthernet0/0' indicates the ACL is applied. What is the root cause?

Accepted Answer

The ACL permits only SSH, but the implicit deny blocks all other traffic, including EIGRP hellos, causing the neighbor relationship to fail and making the loopback unreachable.. The ACL only permits TCP port 22 (SSH) but implicitly denies all other traffic, including routing protocol packets and ICMP. If the SSH traffic is sourced from R2's interface IP, it may be permitted, but if the loopback is not reachable due to routing protocol being blocked, SSH fails.

Answer

The ACL is applied inbound, so it filters traffic entering R1; SSH traffic from R2 to R1's loopback is outbound from R2, so it is not affected.

Answer

R2's SSH client uses a source port that is not TCP 22.

Answer

R1's loopback interface has a separate ACL that blocks SSH.

Question 11

A network uses Control Plane Policing (CoPP) to protect the router. Router R1 has CoPP policy applied that rate-limits all traffic to 1 Mbps. R1 shows: 'show policy-map control-plane' indicates drops for EIGRP packets. R1's EIGRP neighbor R2 is flapping. What is the root cause?

Accepted Answer

The CoPP policy rate-limits EIGRP packets to 1 Mbps, but EIGRP hellos are small and frequent; the rate-limit may still drop them if the policer is not properly configured for burst.. CoPP rate-limits control plane traffic, including EIGRP hellos. If the rate is too low, hellos are dropped, causing the neighbor relationship to flap.

Answer

R2 is sending too many EIGRP packets, exceeding the rate-limit.

Answer

R1 has an ACL that blocks EIGRP packets before they reach the control plane.

Answer

The CoPP policy is applied to the wrong interface.

Question 12

A network engineer runs the following command to troubleshoot an EIGRP issue:

R1# debug eigrp packets hello

*Mar  1 00:05:23.123: EIGRP: received packet with MD5 authentication, key id = 1
*Mar  1 00:05:23.123: EIGRP: int GigabitEthernet0/0, src 10.1.1.2 dst 224.0.0.10, seq 0, ttl 1, opcode = 1 (Hello)
*Mar  1 00:05:23.123: EIGRP: authentication failed for packet from 10.1.1.2, key id = 1, integrity check failed

What does this output indicate?

Accepted Answer

The MD5 key ID or key string does not match between R1 and 10.1.1.2, preventing neighbor formation.. The debug shows a received EIGRP Hello packet with MD5 authentication, but the integrity check fails. This indicates a mismatch in the authentication key or key string between R1 and the neighbor 10.1.1.2.

Answer

The EIGRP neighbor relationship is up, but authentication is failing intermittently.

Answer

EIGRP is using plain-text authentication and the key is incorrect.

Answer

The neighbor 10.1.1.2 is not configured for EIGRP authentication.

Question 13

A network engineer runs the following command to troubleshoot an EIGRP issue:

R1# show ip eigrp topology 10.1.1.0/24

IP-EIGRP (AS 100): Topology entry for 10.1.1.0/24
  State: Passive, Query origin flag: 1, 1 Successor(s), FD is 131072
  Routing Descriptor Blocks:
  10.1.2.2 (GigabitEthernet0/0), from 10.1.2.2, Send flag: 0x0
      Composite metric: (131072/130816), Route is Internal
      Vector metric:
        Minimum bandwidth is 10000 Kbit
        Total delay is 100 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1
  10.1.3.3 (GigabitEthernet0/1), from 10.1.3.3, Send flag: 0x0
      Composite metric: (131328/131072), Route is Internal
      Vector metric:
        Minimum bandwidth is 10000 Kbit
        Total delay is 200 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 2

What does this output indicate?

Accepted Answer

Both paths are feasible successors, but only the first is installed in the routing table.. The output shows two feasible successors for 10.1.1.0/24. The first entry (via 10.1.2.2) is the successor with FD 131072, and the second (via 10.1.3.3) is a feasible successor with RD 131072, which is equal to the FD, so it meets the feasibility condition.

Answer

Only one path is available; the second path is a backup that is not used.

Answer

Both paths are installed in the routing table for load balancing.

Answer

The route is in active state, indicating a query is in progress.

Question 14

A network engineer runs the following command to troubleshoot an EIGRP issue:

R1# show ip eigrp topology all-links

IP-EIGRP Topology Table for AS 100

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - Reply status, s - sia Status

P 10.1.1.0/24, 1 successors, FD is 131072
         via 10.1.2.2 (131072/130816), GigabitEthernet0/0
         via 10.1.3.3 (131328/131072), GigabitEthernet0/1
P 10.2.2.0/24, 1 successors, FD is 131072
         via 10.1.2.2 (131072/130816), GigabitEthernet0/0
A 10.3.3.0/24, 0 successors, FD is Infinity
         via 10.1.2.2 (4294967295/4294967295), GigabitEthernet0/0
         via 10.1.3.3 (4294967295/4294967295), GigabitEthernet0/1

What does this output indicate?

Accepted Answer

The route 10.3.3.0/24 is stuck-in-active because replies have not been received from all neighbors.. The route 10.3.3.0/24 is in Active state with no successors and FD set to Infinity, meaning EIGRP is actively querying neighbors for this route and has not yet received a reply. The metric of 4294967295 indicates an unreachable route.

Answer

The route 10.3.3.0/24 is passive and has two feasible successors.

Answer

The route 10.3.3.0/24 is learned via both neighbors with equal metrics.

Answer

The route 10.3.3.0/24 is installed in the routing table via both neighbors.

Question 15

Which of the following is the correct formula for EIGRP composite metric calculation using default K values?

Accepted Answer

metric = bandwidth + delay. With default K values (K1=1, K2=0, K3=1, K4=0, K5=0), the composite metric reduces to metric = bandwidth + delay.

Answer

metric = bandwidth * delay

Answer

metric = bandwidth + delay + reliability

Answer

metric = bandwidth + delay + load