ACSP - Aruba Certified Switching Professional VLANs and Link Aggregation Questions and Answers — Questions and Answers
Question 1: A network administrator is configuring a link aggregation group (LAG) between two ArubaOS-CX switches. The administrator wants to ensure that the LAG is formed only if LACP negotiations are successful between the two switches. Which LACP mode combination should be configured on the two switches to achieve this?
- Active on one switch and Passive on the other switch. (Correct answer)
- Static on both switches.
- Passive on both switches.
- Active on both switches and Static on one switch.
Correct answer: Active on one switch and Passive on the other switch.
For a dynamic LACP LAG to form, at least one side must be in 'active' mode to initiate the LACP negotiation. An active-passive combination is a standard and valid configuration where the active side sends LACPDU packets, and the passive side responds, successfully forming the aggregation. Two passive sides will never form a LAG because neither will initiate the negotiation.
Question 2: An engineer is setting up a new access switch that connects to a distribution switch using two bundled links. The distribution switch is configured for a dynamic LACP LAG. The new access switch is unconfigured (factory default). To allow the access switch to boot up, obtain a DHCP address, and download its configuration via Zero-Touch Provisioning (ZTP), what feature must be enabled on the distribution switch's LAG interface?
- Spanning Tree Protocol (STP) PortFast
- Static LAG
- LACP fallback-static (Correct answer)
- VLAN trunking
Correct answer: LACP fallback-static
LACP fallback-static is designed for scenarios like ZTP or PXE booting. When the distribution switch does not receive LACP PDUs from the downstream device (like a factory-default switch), LACP fallback-static allows one port of the LAG to come up as a normal, non-bonded interface. This enables the new switch to communicate on the network to get its configuration.
Question 3: A network administrator configures a Layer 2 LAG between two ArubaOS-CX switches to carry traffic for multiple VLANs. Which command is used on the logical LAG interface to specify which VLANs are permitted to cross the aggregated link?
- vlan access <vlan-id>
- vlan trunk native <vlan-id>
- vlan trunk allowed <vlan-list> (Correct answer)
- vlan tagged <vlan-list>
Correct answer: vlan trunk allowed <vlan-list>
On ArubaOS-CX switches, when an interface (including a logical LAG interface) is configured as a trunk to carry multiple VLANs, the `vlan trunk allowed` command is used to define the specific list of VLANs that are permitted to traverse that trunk.
Question 4: Which of the following is a primary advantage of using dynamic LACP over a static link aggregation group (LAG)?
- It supports more member ports in the LAG.
- It provides faster per-packet load balancing.
- It offers lower configuration overhead.
- It provides active detection of link failures and misconfigurations. (Correct answer)
Correct answer: It provides active detection of link failures and misconfigurations.
Dynamic LACP uses Link Aggregation Control Protocol Data Units (LACPDUs) to actively communicate between peer switches. This allows it to detect misconfigurations (like a mismatched cable) or unidirectional link failures that a static LAG cannot, as static LAGs do not exchange any control information.
Question 5: An ArubaOS-CX switch has a two-port LAG configured. An administrator wants to understand how traffic is being distributed across the member links. By default, what information does an ArubaOS-CX switch use in its hashing algorithm for link aggregation load balancing?
- Source and Destination MAC addresses only.
- Layer 4 TCP/UDP ports only.
- Source and Destination IP addresses. (Correct answer)
- A round-robin algorithm based on packet arrival.
Correct answer: Source and Destination IP addresses.
In ArubaOS-CX, the default hashing algorithm for load balancing traffic across the member ports of a LAG uses the Layer 3 source and destination IP addresses of the packets. While other parameters can be configured, this is the default behavior.
Question 6: A network engineer is configuring an interface on an ArubaOS-CX switch that will connect to an end-user's PC. The PC needs to be placed in VLAN 100. The interface should only accept untagged traffic and place it into VLAN 100. What command correctly configures the interface for this requirement?
- vlan trunk native 100
- vlan access 100 (Correct answer)
- vlan trunk allowed 100
- vlan tagged 100
Correct answer: vlan access 100
The `vlan access 100` command configures a switch port as an access port. An access port is a member of a single VLAN and handles untagged traffic. Any untagged frames received on this port are assigned to VLAN 100, and any frames sent out of this port for VLAN 100 are sent untagged, which is what standard end devices like PCs expect.
ACSP - Aruba Certified Switching Professional VLANs and Link Aggregation Questions and Answers
A network administrator is configuring a link aggregation group (LAG) between two ArubaOS-CX switches.
The administrator wants to ensure that the LAG is formed only if LACP negotiations are successful between the two switches.
Which LACP mode combination should be configured on the two switches to achieve this?