300-410 Practice Test 30 — 15 Questions

Question 1

An engineer configures unicast Reverse Path Forwarding (uRPF) in strict mode on an interface connected to a network with asymmetric routing. Users report intermittent connectivity issues. Which is the most likely explanation?

Accepted Answer

Asymmetric routing causes packets to arrive on an interface that is not the best return path, so uRPF drops them.. Strict mode uRPF checks that the source IP of incoming packets has a route back through the same interface. With asymmetric routing, packets may arrive on an interface that is not the best return path, causing uRPF to drop them. Loose mode would allow asymmetric routing but still check for a route.

Answer

The uRPF configuration is missing the 'allow-default' option.

Answer

The routing table does not have a route for the source IP.

Answer

The interface has multiple IP addresses.

Question 2

An engineer must configure a Cisco IOS router to log messages to a syslog server at 192.168.1.100 with a severity level of 3 (errors) and above, while also ensuring that console messages are limited to severity 5 (notifications) and above. Which TWO configuration changes are required? (Choose TWO.)

Accepted Answer

Configure 'logging host 192.168.1.100' and 'logging trap errors'.. The 'logging host' command specifies the syslog server and optionally the severity level. The 'logging console' command sets the console logging level. The 'logging trap' command sets the severity for syslog server messages, but when using 'logging host' with a level, it overrides the global trap level for that host. The 'logging buffered' command affects buffer logging, not console or syslog. The 'logging source-interface' sets the source IP but does not affect severity.

Answer

Configure 'logging console debugging' to ensure all messages are seen on console.

Answer

Configure 'logging buffered errors' to store logs locally.

Answer

Configure 'logging source-interface Loopback0' to use a specific source IP.

Question 3

Which THREE commands can be used to verify the current NTP synchronization status and configuration on a Cisco IOS router? (Choose THREE.)

Accepted Answer

show ntp status. The 'show ntp status' displays the clock synchronization state, stratum, and reference. The 'show ntp associations' shows configured NTP peers/servers and their reachability. The 'show ntp packets' is not a valid command. The 'show ntp statistics' provides packet statistics. The 'show clock' shows the current time but not NTP details. The 'debug ntp packets' is a debug command, not a show command.

Answer

show ntp packets

Answer

show clock detail

Question 4

Which TWO statements about the 'ip domain-lookup' and DNS configuration on a Cisco IOS router are true? (Choose TWO.)

Accepted Answer

The 'ip name-server' command can specify up to six DNS servers.. The 'ip domain-lookup' command enables DNS resolution; it is enabled by default. The 'ip name-server' command specifies DNS servers. The 'ip domain-list' command adds a domain suffix to be appended to unqualified names. The 'ip host' command creates a static host entry. The 'show hosts' command displays both static and dynamically learned DNS entries. The 'ip domain-lookup' must be enabled for dynamic DNS resolution to work.

Answer

The 'ip domain-lookup' command is disabled by default on Cisco IOS routers.

Answer

The 'ip host' command creates a dynamic DNS entry that can be overwritten by a DNS server.

Answer

The 'show hosts' command displays only statically configured host entries.

Question 5

An engineer configures OSPF on two directly connected routers with MTU 1500 on one interface and MTU 1600 on the other. The OSPF adjacency remains stuck in EXSTART/EXCHANGE state. Which is the most likely explanation?

Accepted Answer

The larger MTU interface sends DBD packets that are too big for the smaller MTU interface, preventing the exchange of LSAs.. OSPF uses the interface MTU in the Database Description (DBD) packets. If the MTU values differ, the receiving router will reject DBD packets larger than its own MTU, causing the adjacency to stall in EXSTART/EXCHANGE. This is a common edge case because many engineers assume OSPF will negotiate MTU automatically.

Answer

OSPF uses TCP, and the MSS mismatch causes the adjacency to fail.

Answer

The MTU mismatch causes a routing loop that prevents the exchange of hello packets.

Answer

The router with the smaller MTU will not send hello packets because it detects the mismatch.

Question 6

A network engineer is troubleshooting why the NMS cannot poll the CPU utilization of router R7 via SNMP. The router has 'snmp-server community cisco RO' configured. The NMS can poll interface statistics and routing table entries successfully. What is the most likely cause?

Accepted Answer

The engineer configured an SNMP view that excludes the CPU utilization OID tree.. CPU utilization OIDs are part of the CISCO-PROCESS-MIB, which may not be loaded by default. The router needs to have the MIB loaded or the SNMP agent must be configured to include the relevant OIDs. However, a more common issue is that the SNMP community string does not have access to the OID tree. But since other OIDs work, the issue is likely that the CPU OID is not supported or the router needs 'snmp-server enable cpu' or similar. Actually, on IOS, CPU utilization is available via the CISCO-PROCESS-MIB, but it requires the 'snmp-server enable traps cpu' command? No, that's for traps. For polling, the MIB is usually available. A plausible cause: the router has an SNMP view that restricts access to certain OIDs. The engineer might have applied a view to the community. But the stem doesn't mention a view. Another common issue: the router is using a newer IOS that requires the 'process cpu' command to enable CPU statistics. Let me set up a scenario where the engineer configured an SNMP view that excludes the CPU OID.

Answer

The router needs the 'snmp-server enable traps cpu' command to allow CPU polling.

Answer

The NMS is using an incorrect OID for CPU utilization; the correct OID is in the CISCO-PROCESS-MIB.

Answer

The router's CPU is not supported for SNMP polling due to hardware limitations.

Question 7

An engineer configures EIGRP named mode on two routers in the same AS. One router uses classic mode configuration. The routers fail to form an adjacency. Which is the most likely explanation?

Accepted Answer

Named mode and classic mode are incompatible and cannot form an adjacency under any circumstances.. EIGRP named mode and classic mode use different packet formats and K-value handling. Named mode defaults to 'k1 1 k2 0 k3 1 k4 0 k5 0' with wide metrics, while classic mode uses the same K values but metric computation differs. The adjacency fails because the routers cannot agree on the metric computation method, even if K values match.

Answer

The K values must match exactly, but named mode defaults to different K values than classic mode.

Answer

Named mode requires authentication, while classic mode does not.

Answer

The routers must be in the same autonomous system number, but named mode uses a different AS number format.

Question 8

An engineer configures iBGP between two routers in the same AS. The BGP table shows the prefix, but it is not installed in the routing table. The IGP does not carry the prefix. Which is the most likely explanation?

Accepted Answer

The BGP synchronization rule is enabled, and the prefix is not in the IGP, so BGP does not install the route.. BGP synchronization rule (default enabled in older IOS versions) requires that the prefix must be present in the IGP before it is installed in the routing table. If the IGP does not carry the prefix, BGP will not install it even if learned via iBGP. This edge case often surprises engineers who assume iBGP routes are always installed.

Answer

The next-hop is unreachable because of a missing static route.

Answer

The BGP route is filtered by an inbound route-map.

Answer

The maximum-paths limit is exceeded.

Question 9

An engineer configures mutual redistribution between OSPF and EIGRP on a router. After a few minutes, routing loops occur. The engineer did not configure route tagging. Which is the most likely explanation?

Accepted Answer

The router redistributes routes from OSPF into EIGRP, and then those routes are redistributed back into OSPF, creating a loop.. Mutual redistribution without route tagging can cause a routing loop because a route redistributed from OSPF into EIGRP may be redistributed back into OSPF, creating a feedback loop. Without a tag to mark the origin, the router cannot distinguish between a route it originated and one it learned from another protocol.

Answer

The seed metric is not configured, causing EIGRP to reject the redistributed routes.

Answer

OSPF has a lower administrative distance than EIGRP, causing route preference issues.

Answer

The router is running both protocols on the same interface, causing a conflict.

Question 10

A network engineer runs the following command on Router R1:

R1# show snmp trap

SNMP Trap: enabled

Trap receiver: 192.168.1.100
    Community: PUBLIC
    Version: 2c
    UDP port: 162
    Enable traps: snmp, interface, bgp

Trap receiver: 192.168.1.200
    Community: PRIVATE
    Version: 2c
    UDP port: 162
    Enable traps: snmp, ospf

Based on this output, which statement is correct?

Accepted Answer

BGP traps will be sent to 192.168.1.100 but not to 192.168.1.200.. The output shows two trap receivers with different enabled traps. The first receiver is configured to receive snmp, interface, and bgp traps. The second receiver is configured for snmp and ospf traps. Both use SNMPv2c with community strings.

Answer

Both receivers will receive OSPF traps.

Answer

The traps are sent using SNMPv3.

Answer

Interface traps are sent to 192.168.1.200.

Question 11

Which SNMP version introduced the use of a User-based Security Model (USM) and View-based Access Control Model (VACM)?

Accepted Answer

SNMPv3. SNMPv3 introduced USM for authentication and encryption, and VACM for fine-grained access control. SNMPv1 and v2c use community strings and do not support these security models.

Answer

SNMPv1

Answer

SNMPv2c

Answer

SNMPv2u

Question 12

An engineer configures a DMVPN Phase 2 network. Spoke-to-spoke tunnels do not form, even though NHRP registration is successful. Which is the most likely explanation?

Accepted Answer

The spoke routers do not have a route to each other's tunnel IP via the hub, so the NHRP shortcut request fails.. In DMVPN Phase 2, spoke-to-spoke tunnels require that the spoke routers have a route to each other's tunnel IP via the hub. Phase 2 uses NHRP redirect and shortcut, but the spoke must have a route pointing to the hub for the destination network. If the spoke's routing table does not have a route to the remote spoke's tunnel IP via the hub, the shortcut will not be triggered.

Answer

The NHRP authentication key is mismatched between spokes.

Answer

The mGRE interface is configured with tunnel mode gre multipoint on the spokes.

Answer

The hub is not configured with 'ip nhrp redirect' and the spokes with 'ip nhrp shortcut'.

Question 13

What is the default SNMP trap queue length on Cisco IOS?

Accepted Answer

10. The default trap queue length is 10 messages. If the queue is full, new traps may be dropped. This can be adjusted with the 'snmp-server queue-length' command.

Answer

100

Answer

Unlimited

Answer

5

Question 14

An engineer configures IPsec between two routers using transform-set esp-aes 256 esp-sha-hmac. The tunnel fails to establish. Debug shows 'transform set proposal mismatch'. Which is the most likely explanation?

Accepted Answer

The other router uses 'esp-aes' without specifying the key length, defaulting to 128-bit, causing a mismatch.. The transform-set must match exactly on both ends, including the encryption and hash algorithms. A common edge case is that one side uses 'esp-aes 256' while the other uses 'esp-aes', which defaults to 128-bit. The mismatch causes the proposal to be rejected.

Answer

The transform-set uses SHA-1, which is not supported by the other router.

Answer

The IPsec proposal includes both esp-aes and esp-3des, causing confusion.

Answer

The transform-set is missing the authentication header.

Question 15

An engineer configures Control Plane Policing (CoPP) on a router to protect the control plane. After applying the policy, OSPF adjacencies go down. The policy includes a class that matches OSPF traffic with a police rate of 1000 pps. Which is the most likely explanation?

Accepted Answer

The OSPF traffic is matched by class-default, which has a low police rate or is set to drop, causing hello packets to be dropped.. CoPP applies to traffic destined to the control plane. If the police rate is too low, legitimate OSPF hello packets may be dropped. However, a more subtle edge case is that the default class (class-default) may have an explicit deny or very low rate, causing all unmatched traffic to be dropped, including OSPF if not explicitly matched.

Answer

The police rate of 1000 pps is too low for OSPF hello packets.

Answer

CoPP only applies to management traffic, not routing protocols.

Answer

The OSPF process is not configured to use the control plane policy.