HPE7-A08 Questions and Answers

DHCP snooping requires to be enabled globally before it will function correctly. If it is not enabled globally, even if enabled on VLAN interfaces, DHCP snooping will not work.

Enabling authorized DHCP servers (A) or trusted interfaces (B) is necessary but only after global enabling.

Enabling DHCP snooping on VLAN (C) is not sufficient without global enablement.

Therefore, enabling DHCP snooping globally is the first step to activate the feature.

The LACP fallback command in Aruba VSX configurations allows the system to continue forwarding traffic even if LACP negotiation fails or is not established. This is useful when provisioning a gateway or link that does not support LACP, ensuring that the port remains operational in a static manner.

It is not specifically for backward compatibility with LACP v1.

It does not relate to operation with a single partner interface.

It also is not about active/passive LACP modes per se.

Therefore, LACP fallback is configured to support provisioning a gateway without LACP.

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When deploying a new Aruba CX 8325 switch to provide gateway and routing services, the L3-apg profile (Layer 3 Aggregation Profile) should be selected instead of the factory default. This profile is designed for switches acting as aggregation or core routers, enabling Layer 3 routing capabilities and optimized configurations for such roles.

The Spine profile (factory default) is optimized for leaf/spine architectures, but may not be ideal for aggregation gateways.

Leaf and L3-core profiles are targeted for different roles.

Using the L3-apg profile helps to ensure the switch is correctly optimized for Layer 3 gateway functions.

When making changes remotely to critical configurations such as Control Plane ACLs on a CX switch, to protect against accidental lockout due to misconfiguration, you should enable checkpoint auto before committing the changes.

Checkpoint auto creates an automatic rollback timer. If the administrator loses connectivity (e.g., because of the ACL change), the system automatically rolls back the change after the timer expires, preventing lockout.

checkpoint commit is used after committing to save the checkpoint explicitly, but it does not provide automatic rollback.

Running checkpoint auto before committing is essential to have the rollback safety net.

When establishing eBGP peering between devices that are not directly connected, the TTL (Time To Live) value of the BGP packets must be increased to allow them to traverse multiple hops. This is achieved by configuring ebgp-multihop, which increases the TTL beyond the default value of 1.

next-hop-self changes the BGP next-hop attribute but is not required for multihop eBGP.

route-reflector is a BGP design feature unrelated to multihop.

address-family ipv4 external is not a standard command on Aruba CX switches.

Therefore, to successfully peer eBGP sessions across multiple hops, ebgp-multihop must be configured.

The customer wants to tunnel traffic from APs through CX switches, similar to what they currently do with a gateway cluster. Aruba’s User-Based Tunneling (UBT) is designed specifically for this use case. UBT allows traffic from wireless and wired clients to be tunneled to a centralized gateway or controller for policy enforcement and traffic inspection.

IPSec and GRE are general tunneling protocols but not Aruba’s recommended solution for AP traffic.

VNBT relates to colorless ports and dynamic segmentation, not tunneling client traffic.

Thus, UBT is the correct tunneling solution for AP traffic through CX switches.

IGMP (Internet Group Management Protocol) supports several message types: Join, Leave, Query, and Report messages to manage multicast group membership.

Join messages indicate a host wants to join a multicast group.

Leave messages indicate a host is leaving a multicast group.

Query messages are sent by routers to discover group members.

Report messages are sent by hosts to indicate membership.

Therefore, the full set of IGMP message types supported includes Join, Leave, Query, and Report.

Options with only Leave and Report or only Join and Query are incomplete.

Dynamic Segmentation (DS) requires certain capabilities on the switches to support user role assignment and traffic segmentation based on identity. The CX 6100 series switches do not support Dynamic Segmentation due to hardware and feature limitations. Therefore, they must be replaced with CX 6300 models, which support DS features natively.

Options involving GRE tunnels or VXLAN tunnels relate to traffic forwarding but do not enable DS on unsupported hardware.

Applying licenses does not upgrade hardware capabilities for DS.

When enabling ARP protection, it is best practice to wait at least a week after enabling DHCP snooping before enabling ARP protection in a live network. This allows the DHCP snooping binding table to stabilize, ensuring ARP protection has accurate IP-MAC bindings, reducing false positives.

Immediate ARP protection may cause legitimate traffic to be dropped.

Lease times and DHCP server utilization are less critical.

This staged approach minimizes disruption.

If both switches are configured with default spanning-tree priorities and both appear as primary root bridges, to have a single spanning tree domain, matching MST configuration (Multiple Spanning Tree) must be created on Core-2 to align with Core-1.

Setting priority to 1 on one switch can help but matching MST configurations is the recommended approach for multiple VLANs.

Creating MST instances on only one switch will not ensure consistency.

Matching MST configurations ensures consistent root bridge election and stable spanning tree.

For a 1 Gbps link between two Aruba CX switches, the appropriate SFP port type is an SFP (Small Form-factor Pluggable). SFP+ and SFP28 are used for higher speeds such as 10 Gbps and 25 Gbps, respectively. QSFP+ is for even higher speeds (40 Gbps).

SFP supports 1 Gbps (1000BASE-X)

SFP+ supports 10 Gbps

SFP28 supports 25 Gbps and above

QSFP+ supports 40 Gbps and above

Therefore, the correct port type for a 1 Gbps link is SFP.

The configuration involves connecting two buildings over fiber using OM4 cabling with a distance of 200 meters. The current optics in use are 25GR (25 Gigabit Rate) optics.

For multimode fiber such as OM4, SR (Short Reach) optics are suitable for distances up to 300 meters. In contrast, LR (Long Reach) optics are typically designed for single-mode fiber and longer distances.

Therefore, to properly support the 200m OM4 fiber link, 25SR optics should be used instead of 25GR (which are often long-reach optics).

10SR and 10LR refer to 10Gbps optics, which do not meet the 25Gbps requirement.

25LR optics are for single-mode fiber and longer distances, not multimode.

Comprehensive Detailed Explanation:

To prevent man-in-the-middle attacks based on Layer 2 (Ethernet) addressing, enabling ARP inspection in the VLAN context is recommended. ARP inspection validates ARP packets and ensures only legitimate ARP responses are forwarded.

Enabling ARP inspection at VLAN level allows granular control.

Interface-level or global context is less typical or supported for ARP inspection on Aruba CX switches.

For BGP in a multi-homed configuration advertising public IP blocks, the AS number should be a valid public AS number allocated by the regional internet registry (RIR). Numbers in the private AS range (64512–65534) are not suitable for public Internet announcements.

63472 falls in the public AS range (16-bit AS numbers below 64512).

64813, 65535, and 65218 are in the private or reserved range.

Therefore, 63472 is an example of a suitable public AS number.

The multicast group address 239.0.0.1 falls within the administratively scoped multicast addresses but overlaps with the Link-Local Multicast address scope (224.0.0.0/24), which is reserved for protocol control traffic and should not be used for application multicast groups. Using an address that overlaps with the Link-Local scope can cause multicast routing and forwarding issues, leading to video streaming clients not receiving the stream.

IGMP snooping version or enabling IGMP without multicast traffic do not cause this issue.

PIM-SM discovery addresses are different multicast addresses.

Colorless ports allow network devices to move or replace endpoints without changing port-level configurations, typically by automatically assigning network policies dynamically to any port.

HPE Aruba’s solution for colorless ports is the VNBT (Virtual Network Boundary Tagging) feature. VNBT allows dynamic segmentation of traffic, so ports can automatically take on the policies assigned to devices regardless of physical port location.

VRRP is a first-hop redundancy protocol and unrelated to port colorlessness.

VSF (Virtual Switching Framework) is for switch stacking.

VRF (Virtual Routing and Forwarding) is for traffic segmentation.

Thus, VNBT is the correct feature to meet colorless port requirements.