300-410 Practice Test 48 — 15 Questions

Question 1

Drag and drop the steps to troubleshoot EIGRP neighbor adjacency formation into the correct order, from first to last.

Accepted Answer

Verify Layer 1 and Layer 2 connectivity between routers. The correct order ensures that you first verify the physical and data link layer, then check IP connectivity, confirm EIGRP is enabled on the correct interfaces, verify the autonomous system number matches, and finally check for any passive interface configuration that might block adjacency.

Question 2

In a 6to4 tunnel, how is the tunnel destination address determined?

Accepted Answer

It is derived from the IPv6 destination address using the 2002::/16 prefix.. In a 6to4 tunnel, the tunnel destination address is automatically derived from the IPv6 destination address by extracting the IPv4 address embedded in the 2002::/16 prefix. Specifically, the first 16 bits of the IPv6 destination are 2002, and the next 32 bits represent the IPv4 address of the remote 6to4 router. This allows the tunnel to be dynamically established without manual configuration of each destination.

Answer

It is manually configured.

Answer

It is obtained via DNS.

Answer

It is the same as the tunnel source.

Question 3

A network engineer is troubleshooting a VRF-Lite deployment where two routers are connected via a trunk link. Each router has two VRFs (VRF_A and VRF_B). The engineer configures subinterfaces on the trunk link, assigning each subinterface to a different VRF. However, traffic between the two routers for VRF_A is not working. The 'show vrf' command shows the VRFs are active. What is the most likely issue?

Accepted Answer

The subinterface on Router1 is configured with 'encapsulation dot1q 10', but the subinterface on Router2 is configured with 'encapsulation dot1q 20'.. For VRF-Lite over a trunk, the subinterfaces on both ends of the link must use the same 802.1Q VLAN ID for the same VRF. If Router1 uses dot1q 10 for VRF_A and Router2 uses dot1q 20, the frames are tagged with different VLANs and each router will drop the other's traffic because the VLANs do not match. This is the most likely cause of the VRF_A traffic failure.

Answer

The 'ip vrf forwarding VRF_A' command is missing on the main interface.

Answer

The 'no ip routing' command is configured globally.

Answer

The 'mtu' command is set differently on the two subinterfaces.

Question 4

A network engineer is troubleshooting a BGP route summarization issue. Router R1 is configured with the 'aggregate-address 192.168.0.0 255.255.252.0' command without any keywords. The engineer notices that the ISP neighbor is receiving both the aggregate route and the more specific routes (192.168.0.0/24, 192.168.1.0/24, etc.), causing the ISP to prefer the specific routes. What should the engineer do to ensure the aggregate route is preferred?

Accepted Answer

Add the 'summary-only' keyword to the aggregate-address command.. The 'aggregate-address' command without keywords advertises both the summary route and all more-specific component routes. Adding the 'summary-only' keyword suppresses the more-specific routes from being advertised to BGP neighbors, leaving only the aggregate. This forces the ISP to use the aggregate since no longer-matching specifics exist.

Answer

Remove the network statements for the specific subnets from the BGP process.

Answer

Configure a route-map to set a higher local preference on the aggregate route.

Answer

Use the 'aggregate-address' command with the 'as-set' keyword.

Question 5

A network engineer runs the following command on Router R1:

R1# show ipv6 mld interface tunnel 0

Tunnel0 is up, line protocol is up
  Internet address is FE80::1
  MLD is enabled on interface
  Current MLD version is 2
  MLD query interval is 125 seconds
  MLD querier timeout is 255 seconds
  MLD max query response time is 10 seconds
  Last member query response interval is 1 second
  MLD activity: 0 joins, 0 leaves
  MLD querying router is FE80::1 (this system)

Based on this output, what can be concluded?

Accepted Answer

There are no multicast listeners on this tunnel interface.. The output shows 'MLD activity: 0 joins, 0 leaves', indicating that no multicast listeners have joined any multicast group on this tunnel interface. Since MLD (Multicast Listener Discovery) is used to track group membership, zero joins means there are no active listeners. Therefore, option C is correct.

Answer

MLD is disabled on this interface.

Answer

This router is not the MLD querier.

Answer

MLD version 1 is in use.

Question 6

Which BGP message type is used to advertise, withdraw, and update routes?

Accepted Answer

UPDATE. The BGP UPDATE message is the only message type that carries routing information — it advertises new routes (NLRI), withdraws previously advertised routes, and includes path attributes. OPEN, KEEPALIVE, and NOTIFICATION serve session establishment and maintenance, not route propagation.

Answer

OPEN

Answer

NOTIFICATION

Answer

KEEPALIVE

Question 7

Which loop prevention mechanism is used by default in RIP within a VRF-Lite configuration?

Accepted Answer

Split horizon. RIP uses split horizon as a default loop prevention mechanism, and this behavior is preserved within VRF-Lite configurations because VRF-Lite simply partitions the routing table without changing RIP's protocol behavior. Split horizon prevents a router from advertising a route back out the interface it learned it from.

Answer

Route poisoning

Answer

Hold-down timer

Answer

TTL expiry

Question 8

A network engineer runs the following command on Router R7:

R7# show logging | include %SYS-2-MALLOCFAIL

*Mar  1 00:05:10.123: %SYS-2-MALLOCFAIL: Memory allocation failed for size 1024, from process 0x12345678, pool Processor
*Mar  1 00:06:20.456: %SYS-2-MALLOCFAIL: Memory allocation failed for size 2048, from process 0x12345678, pool Processor
*Mar  1 00:07:30.789: %SYS-2-MALLOCFAIL: Memory allocation failed for size 512, from process 0x12345678, pool Processor

Based on this output, what is the most likely problem?

Accepted Answer

The router has a memory leak or is running out of memory in the Processor pool.. The %SYS-2-MALLOCFAIL messages indicate that the router failed to allocate memory from the Processor pool for various sizes. Repeated allocation failures across different sizes strongly suggest a memory leak or exhaustion in that pool, which is a critical resource issue. This matches option A.

Answer

The router is experiencing high CPU utilization due to routing protocol updates.

Answer

The router's logging buffer is full and cannot store new messages.

Answer

The router has a hardware failure in the memory module.

Question 9

A network engineer configures SNMPv3 with authentication only (no privacy) on a router. The NMS can poll the router successfully. Later, the engineer adds the 'priv' option to the user configuration. The NMS now fails to poll the router. Which is the most likely explanation?

Accepted Answer

The NMS is still configured with the old credentials that do not include the privacy protocol and key.. When the engineer adds the 'priv' option to the SNMPv3 user configuration on the router, the security level changes from authNoPriv to authPriv. The NMS must be updated with the matching privacy protocol (e.g., AES or DES) and the corresponding privacy key. If the NMS still uses the old credentials without the privacy parameters, the authentication will succeed but the privacy decryption will fail, causing the NMS to reject the response and report a polling failure.

Answer

The router's SNMP engine ID changed when the user was modified.

Answer

The privacy protocol (e.g., AES) is not supported on the router.

Answer

The NMS must restart to recognize the new security level.

Question 10

An engineer enables uRPF (unicast Reverse Path Forwarding) in strict mode on an interface connected to a DMVPN spoke. The spoke has multiple tunnels and receives traffic from the hub with a source IP that is not the best reverse path. Unexpectedly, the spoke drops all traffic from the hub, even though the hub is reachable via the tunnel. Which is the most likely explanation?

Accepted Answer

uRPF strict mode requires the reverse path to be via the same interface; asymmetric routing causes drops.. uRPF strict mode verifies that the source IP of an incoming packet is reachable via the same interface the packet arrived on, using the FIB. In a DMVPN spoke scenario, traffic from the hub may arrive on a tunnel interface while the reverse path to the hub's source IP points to a different tunnel or the physical interface, causing strict mode to drop the packets. This is the classic asymmetric routing failure mode for strict uRPF.

Answer

The hub's IP address is not in the routing table, so uRPF drops the packet.

Answer

uRPF must be configured with the `allow-default` option to accept packets with default route.

Answer

uRPF is not supported on tunnel interfaces; it must be applied on the physical interface.

Question 11

An engineer is troubleshooting an IPv6 connectivity issue where hosts on VLAN 10 cannot reach the internet. The switch is configured with IPv6 First Hop Security features including RA Guard and DHCPv6 Guard. The legitimate router is connected to port Gi1/0/1. The engineer notices that the router is sending RAs, but hosts are not receiving them. The switch shows that RA Guard is dropping packets on port Gi1/0/1. What is the most likely misconfiguration?

Accepted Answer

The RA Guard policy is configured with 'device-role host' on port Gi1/0/1, which causes the switch to drop all RAs received on that port.. RA Guard drops Router Advertisements (RAs) on ports where the policy's 'device-role' is set to 'host'. On port Gi1/0/1, the legitimate router is connected, but if the RA Guard policy incorrectly assigns 'device-role host' to that port, the switch will treat the router as a host and drop all incoming RAs, preventing hosts on VLAN 10 from receiving them. This matches the symptom where the router sends RAs but hosts do not receive them, and the switch reports RA Guard dropping packets on that port.

Answer

DHCPv6 Guard is configured on port Gi1/0/1, blocking the router's DHCPv6 server messages.

Answer

IPv6 Source Guard is enabled on the VLAN, and the router's IPv6 address is not in the binding table.

Answer

The switch has IPv6 unicast-routing enabled, and it is sending its own RAs, causing a conflict.

Question 12

Examine the following configuration:

logging host 10.1.1.1
logging host 10.1.1.2
logging host 10.1.1.3
logging origin-id hostname
logging facility local7

What is the purpose of the 'logging origin-id hostname' command?

Accepted Answer

It causes the syslog messages to include the router's hostname as the origin, overriding the default IP address.. The logging origin-id hostname command changes the origin identifier in syslog messages from the default (the source IP address of the sending interface) to the router's configured hostname. This makes it easier for the syslog server to identify which device sent the message, especially when the source IP changes or is NATed. It does not affect timestamps, message filtering, or authentication.

Answer

It sets the syslog message format to include the hostname in the timestamp field.

Answer

It configures the router to send syslog messages only when the hostname changes.

Answer

It is used to authenticate syslog messages using the hostname as a key.

Question 13

Which of the following best describes the behavior of BGP when an 'aggregate-address' command is used without the 'summary-only' keyword?

Accepted Answer

The aggregate route is advertised, and all more specific routes are also advertised.. Without the summary-only keyword, BGP advertises both the aggregate route and the more specific routes that are in the BGP table.

Answer

Only the aggregate route is advertised.

Answer

The aggregate route is not advertised unless a network command exists for it.

Answer

The more specific routes are withdrawn from the BGP table.

Question 14

Which THREE symptoms indicate a problem with route redistribution causing suboptimal routing or routing loops? (Choose THREE.)

Accepted Answer

Routing loops occur where packets traverse multiple routers repeatedly.. Route redistribution problems manifest in specific, observable ways. Option A is correct because a routing loop caused by mutual redistribution (for example, redistributing routes back and forth between OSPF and EIGRP without proper filtering or administrative distance/tagging) makes packets traverse multiple routers repeatedly until the TTL expires. Option B is correct because suboptimal routing occurs when a redistributed route's metric or administrative distance makes a longer path appear preferable to a shorter path that already exists within the same routing domain. Option D is correct because missing reachability to networks that exist in the redistribution router's table typically indicates a redistribution filter, missing redistribute statement, or a seed metric problem preventing those prefixes from being advertised into the target protocol. Option C is not a symptom of redistribution issues since low CPU utilization is normal and healthy, not indicative of loops or suboptimal paths. Option E is not a symptom either, because stable and fast-converging routing tables describe correct operation rather than a redistribution fault.

Answer

CPU utilization on the redistribution router is consistently below 50%.

Answer

The routing table on all routers is stable and converges quickly after a topology change.

Question 15

Examine the following OSPF configuration on router R1:

router ospf 1
 network 10.0.0.0 0.255.255.255 area 0
 network 192.168.1.0 0.0.0.255 area 1

What is the effect of this configuration?

Accepted Answer

All interfaces with IP addresses in the 10.0.0.0/8 range will be enabled for OSPF in area 0, and interfaces in 192.168.1.0/24 will be in area 1.. The OSPF network statements use wildcard masks to match interfaces. The first statement 'network 10.0.0.0 0.255.255.255 area 0' matches any interface with an IP in 10.0.0.0/8 and places it in area 0. The second statement 'network 192.168.1.0 0.0.0.255 area 1' matches interfaces in 192.168.1.0/24 and places them in area 1. This is valid OSPF configuration; a single process can have interfaces in multiple areas (it becomes an ABR).

Answer

Only the interface with IP 10.0.0.1 will be in area 0; all other 10.x.x.x interfaces are ignored.

Answer

The configuration is invalid because OSPF process 1 cannot have two network statements in different areas.

Answer

The configuration will cause a routing loop between area 0 and area 1.