Test 3 - CCNA 2

A PC is to access a web server on another network. Which inter-VLAN method will provide the highest bandwidth at Layer 3 and also provide a default gateway for the PC?

• multilayer switch with routing enabled

• router on a stick

• trunked interface between the router and the switch

• multiple physical interfaces on the router, all connected to a Layer 2 switch

Answer explanation

Explanation: A router-on-a-stick design is the same as having a trunked interface between the router and the switch. This design works, but does not scale well because all VLANs must traverse the one connection between the router and the switch. Multiple physical interfaces on the router would be faster than the router-on-a-stick design, but a router has a limited number of physical interfaces. Layer 3 switches with routing enabled have more Ethernet ports as well as the ability to route.

Which port state will switch ports immediately transition to when configured for PortFast?

• forwarding

• blocking

• listening

• learning

Answer explanation

Explanation: PortFast allows a switch port to bypass the listening and learning states and transition immediately to the forwarding state.

After the election of the root bridge has been completed, how will switches find the best paths to the root bridge?

• Each switch will analyze the port states of all neighbors and use the designated ports to forward traffic to the root.

• Each switch will analyze the sum of all port costs to reach the root and use the path with the lowest cost.

• Each switch will analyze the sum of the hops to reach the root and use the path with the fewest hops.

• Each switch will analyze the BID of all neighbors to reach the root and use the path through the lowest BID neighbors.

Answer explanation

Explanation: After the election of a root bridge has occurred, each switch will have to determine the best path to the root bridge from its location. The path is determined by summing the individual port costs along the path from each switch port to the root bridge.

What value determines the root bridge when all switches connected by trunk links have default STP configurations?

Answer explanation

Explanation: When all switches are configured with the same default bridge priority, the MAC address becomes the deciding factor for the election of the root bridge. All links on the same VLAN will also have the same extended system ID so this will not contribute to determine which switch is the root for that VLAN.

During the implementation of Spanning Tree Protocol, all switches are rebooted by the network administrator. What is the first step of the spanning-tree election process?

• All the switches send out BPDUs advertising themselves as the root bridge

• Each switch determines the best path to forward traffic

• Each switch determines what port to block to prevent a loop from occurring

• Each switch with a lower root ID than its neighbor will not send BPDUs

Answer explanation

Explanation: After a Cisco switch boots, it will send out BPDUs containing its individual BID and the root ID for the network. By default, the initial root ID at bootup will be the ID of that individual switch. After a root bridge is elected, port states and paths are chosen.

Which three port states are used by Rapid PVST+? (Choose three.)

• listening

• learning

• forwarding

• discarding

• blocking

Answer explanation

Explanation: The Rapid PVST+ port states are discarding, learning, and forwarding.

When PVST is running over a switched network, which port state can participate in BPDU frame forwarding based on BPDUs received, but does not forward data frames?

Answer explanation

Explanation: Ports in the blocking state are nondesignated ports and do not participate in frame forwarding. Ports in the listening state can participate in BPDU frame forwarding according to received BPDU frames, but do not forward data frames. Ports in the forwarding state forward data frames and send and receive BPDU frames. Ports in the disabled state are administratively disabled.

An administrator is troubleshooting a switch and wants to verify if it is a root bridge. What command can be used to do this?

Which three components are combined to form a bridge ID? (Choose three.)

• Bridge priority

• Cost

• Extended system ID

• MAC address

• Port ID

Answer explanation

Explanation: The three components that are combined to form a bridge ID are bridge priority, extended system ID, and MAC address.

What is an advantage of using STP in a LAN?

• It combines multiple switch trunk links into a logical port channel link to increase bandwidth.

• It decreases the size of the failure domain.

• It provides firewall services to protect the LAN.

• It temporarily disables redundant paths to stop Layer 2 loops.

Answer explanation

Explanation: STP allows redundant physical connections between Layer 2 devices without creating Layer 2 loops by disabling ports that could create a loop.