350-401 Practice Test 35 — 15 Questions

Question 1

Which two statements about queuing and congestion management are true? (Choose two.)

Accepted Answer

CBWFQ allows you to define multiple classes and assign each a guaranteed minimum bandwidth.. CBWFQ provides guaranteed bandwidth to classes, while LLQ adds a strict priority queue for delay-sensitive traffic. WFQ is the default on low-speed interfaces. FIFO is used on high-speed interfaces by default. Tail drop is the default drop policy for FIFO and CBWFQ queues.

Answer

Weighted Fair Queuing (WFQ) is the default queuing mechanism on all Cisco router interfaces.

Answer

Tail drop is the only drop policy available for CBWFQ queues.

Answer

FIFO queuing provides per-class bandwidth guarantees.

Question 2

An engineer is troubleshooting QoS on a Cisco ASR 1002 router. The router is configured with a policy map that includes a class for voice with a priority command. During congestion, the engineer notices that voice traffic is being dropped even though the priority queue is not congested. The router logs show 'QoS: priority queue overflow'. What is the most likely cause?

Accepted Answer

The priority queue has a default policer that drops traffic exceeding a certain rate. The 'priority queue overflow' log message indicates that the priority queue itself is dropping packets due to exceeding its configured or default policer rate. On Cisco ASR 1000 series routers, a priority class without an explicit 'police' command still has a default policer that limits the priority queue to a percentage of the interface bandwidth (often 33% by default). When voice traffic exceeds this implicit rate, packets are dropped even if the queue depth is not full, because the policer enforces a strict rate limit.

Answer

The interface bandwidth is set too low, causing the priority queue to be under-provisioned

Answer

The class map is not matching the voice traffic correctly

Answer

The router is using WRED on the priority queue

Question 3

Drag and drop each DSCP PHB on the left to its matching queue treatment on the right.

Accepted Answer

EF: Strict priority queue, low latency. EF is for low-latency traffic (strict priority). AF uses four classes with drop probabilities. CS is backward-compatible with IP precedence. BE is best-effort with no guarantees. DF is the default PHB (same as BE).

Question 4

Drag and drop each QoS model on the left to its matching characteristic on the right.

Accepted Answer

IntServ: Uses RSVP to reserve resources per flow. IntServ uses RSVP for per-flow signaling, DiffServ uses DSCP markings for per-hop behavior, Best Effort provides no guarantees, IntServ is not scalable for large networks, DiffServ offers classification and policing at the edge.

Question 5

What is the maximum hop count for EIGRP?

Accepted Answer

255. EIGRP uses a maximum hop count of 255 to prevent routing loops, as defined in RFC 7868. This is a hard-coded limit in the protocol, and routes with a hop count exceeding 255 are considered unreachable.

Answer

15

Answer

224

Answer

Unlimited

Question 6

Which three statements about STP topology changes and convergence are true? (Choose three.)

Accepted Answer

A switch that detects a topology change sends a TCN BPDU toward the root bridge.. When a topology change occurs in 802.1D STP, the switch that detects the change sends a TCN BPDU toward the root bridge. The root bridge then sets the TC flag in its BPDUs, causing all switches to shorten their MAC address aging timers to flush stale entries. This process ensures rapid convergence of the forwarding database. The Max Age timer is used to age out BPDU information, not to flush MAC addresses. The forward delay timer is used during listening and learning states, not directly for MAC aging.

Answer

The Max Age timer is used to flush MAC address entries during a topology change.

Answer

The forward delay timer determines how long a switch waits before transitioning from listening to learning state.

Question 7

Drag and drop each SNMPv3 security level on the left to its matching protection description on the right.

Accepted Answer

noAuthNoPriv: No authentication and no encryption. noAuthNoPriv provides no authentication or encryption; authNoPriv provides authentication only; authPriv provides both authentication and encryption.

Question 8

Which three statements about Cisco QoS queuing and scheduling are true? (Choose three.)

Accepted Answer

Strict priority queuing ensures that voice traffic is always sent before other traffic.. Queuing manages packets when output is congested, and scheduling determines the order of transmission. Cisco uses multiple queues (e.g., 4 queues on Catalyst switches) with strict priority or weighted round-robin (WRR). Option A is correct because strict priority queue (PQ) ensures low-latency for voice. Option B is correct because WRR (or shaped round robin) is used for non-priority queues. Option C is correct because the default queue is usually queue 1 (or the best-effort queue). Option D is incorrect because tail drop is a congestion avoidance mechanism applied to a queue, not a scheduling method. Option E is incorrect because scheduling occurs on the egress interface, not ingress.

Answer

Tail drop is a scheduling algorithm that determines which queue to service next.

Answer

Queuing and scheduling are performed on the ingress interface before routing decisions.

Question 9

Which three statements about the Differentiated Services (DiffServ) QoS model are true? (Choose three.)

Accepted Answer

DiffServ uses the 6-bit DSCP field in the IP header to mark packets, allowing up to 64 different classes of service.. DiffServ is a class-based model that uses the DSCP field in the IP header to classify traffic. It provides per-hop behavior (PHB) and is scalable because core routers only need to inspect the DSCP field. The model does not guarantee end-to-end bandwidth reservation like IntServ does; instead, it relies on traffic conditioning at the edge.

Answer

In DiffServ, core routers perform complex classification and marking based on deep packet inspection.

Answer

DiffServ requires end-to-end signaling using RSVP to reserve bandwidth along the path.

Question 10

Drag and drop each traffic shaping or policing characteristic on the left to its correct description on the right.

Accepted Answer

Traffic shaping: Buffers excess traffic to smooth output rate. Traffic shaping buffers excess traffic to smooth output rate. Policing drops or marks excess traffic. Shaping introduces delay; policing does not. Shaping uses a token bucket; policing uses a token bucket. Shaping is applied outbound; policing is typically inbound.

Question 11

Drag and drop each STP protection feature on the left to its matching purpose on the right.

Accepted Answer

PortFast: Immediately transitions a port to forwarding state. PortFast moves a port to forwarding immediately; BPDU Guard err-disables a port upon BPDU reception; Root Guard prevents a port from becoming root; Loop Guard prevents alternate/backup ports from transitioning to forwarding.

Question 12

Which two statements about Rapid PVST+ are true? (Choose two.)

Accepted Answer

Rapid PVST+ uses a proposal/agreement handshake to achieve rapid convergence.. Rapid PVST+ is an enhancement of the original 802.1D STP that provides faster convergence by using a proposal/agreement handshake. It runs a separate instance of RSTP for each VLAN, enabling per-VLAN load balancing. The UplinkFast feature is not needed because RSTP already handles uplink convergence quickly. The root bridge is elected based on bridge priority, not MAC address alone. Port roles include alternate and backup, not just designated and root.

Answer

Rapid PVST+ requires the UplinkFast feature to be enabled for fast uplink convergence.

Answer

In Rapid PVST+, the root bridge is elected based on the lowest MAC address only.

Answer

Rapid PVST+ supports only two port roles: designated and root.

Question 13

Drag and drop the steps of STP path cost manipulation for load balancing into the correct order, from first to last.

Accepted Answer

Identify redundant links in the topology. To load balance with STP, first identify redundant links. Then change the path cost on one switch's port to make it less preferred. This alters the root port selection. The switch recalculates the spanning tree, and traffic is redirected to the lower-cost path. Finally, verify the new root port and forwarding state.

Question 14

Drag and drop the steps of Layer 3 EtherChannel (routed port-channel) setup into the correct order, from first to last.

Accepted Answer

Create port-channel interface with no switchport. Layer 3 EtherChannel setup requires creating port-channel interface, assigning IP, adding member ports with no switchport, configuring channel-group, and finally verifying routing.

Question 15

Which three statements about QoS trust boundaries and marking are true? (Choose three.)

Accepted Answer

The 'mls qos trust cos' command configures the switch to trust the CoS marking on incoming packets.. The trust boundary defines where the device trusts or re-marks QoS markings. Typically, the boundary is at the access layer switch. The 'mls qos trust' command sets trust. By default, Cisco switches do not trust CoS or DSCP; they must be configured. Trust can be extended to IP phones via CDP. Marking can be done at Layer 2 (CoS) or Layer 3 (DSCP).

Answer

By default, Cisco Catalyst switches trust the CoS value received from connected devices.

Answer

Marking at Layer 2 uses DSCP values in the IP header.