Answer Area:

Advertise your company ' s public address space to a service provider: eBGP

Connecting to the Internet over a single service provider connection: Static Routing

Connecting to multiple service providers and learning different routes from each one: eBGP

Resilient and scalable routing for networks within an organization using route reflectors: iBGP

Resilient routing for a large campus network that is efficient and easily scalable: OSPF

In AOS-CX design, selecting the right routing protocol is based on the boundary of the administrative control and the required scale.

Advertise public address space to a service provider (eBGP): External BGP (eBGP) is the industry-standard protocol used to exchange routing information between different Autonomous Systems (AS). To let the world know how to reach your public IP block, you must " speak " eBGP with your ISP.

Single service provider connection (Static Routing): When a network has only one exit point (a " stub " connection) to the Internet, dynamic protocols are unnecessary. A simple default static route (0.0.0.0/0) pointing to the ISP gateway is the most efficient and least resource-intensive method.

Multiple service providers / Multi-homing (eBGP): When you have two or more ISPs, your switch needs to make a decision on which path is better based on attributes like AS-Path length or MED. eBGP is required here to receive and process these external path attributes.

Internal organization routing with route reflectors (iBGP): Internal BGP (iBGP) is used to carry BGP prefixes within an AS. Because iBGP requires a " Full Mesh " by default (every router connected to every other router), it does not scale well. Route Reflectors are the architectural solution used to allow a central switch to reflect routes to others, ensuring scalability within the organization.

Large campus network (OSPF): Open Shortest Path First (OSPF) is a Link-State Interior Gateway Protocol (IGP). It is the preferred choice for Aruba campus environments because of its fast convergence, hierarchical design (Areas), and ability to handle large numbers of internal subnets efficiently.

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.

Backing up the switch configuration to a remote Linux SFTP server requires using the copy command with the correct protocol (SFTP in this case), username, server IP, filename, and optionally the VRF to route management traffic.

Option A uses SCP and vrf default but the question mentions SFTP server, so SFTP protocol should be used.

Option B is a server-side command (not the switch).

Option C correctly uses copy startup-config sftp://user@192.168.1.100/switch_config.cfg vrf mgmt which backs up the startup-config via SFTP using the management VRF.

Option D is also a server-side command.

Using vrf mgmt is required because the management IP is in a separate VRF on CX switches.

In the world of IP Multicast, the address range is strictly categorized by the IANA. Understanding these boundaries is a core requirement for the ACP-S switching exam.

Link-Local Multicast (224.0.0.0/24): The address used in the scenario, 224.0.0.100 , falls within the " Local Network Control Block " (224.0.0.0 to 224.0.0.255). These addresses are reserved for protocol traffic that is intended to stay within a single broadcast domain (Layer 2). Examples include OSPF (224.0.0.5) and RIPv2 (224.0.0.9).

The Routing Restriction: By design and industry standard, Layer 3 switches and routers do not forward traffic addressed to the 224.0.0.0/24 range. This is a hard-coded behavior to prevent control plane protocols from leaking into other parts of the network. Even if you enable PIM (Protocol Independent Multicast) and IGMP on all SVIs, the switch will drop these packets at the Layer 3 boundary.

The Solution: To route multicast traffic between VLAN 100 and VLANs 200/300, the application must use a group address from the administratively scoped or globally scoped ranges (e.g., 239.0.0.0/8 or 224.0.1.0 and above).

Why Option D is insufficient: While enabling IGMP and PIM on the SVIs is a necessary step for routable multicast, it will not overcome the fundamental architectural block placed on the 224.0.0.0/24 link-local range.

To resolve this QoS mapping issue on AOS-CX , you must understand the hierarchy of Trust Levels and how they interact with Link Aggregation Groups (LAGs) .

Trust Hierarchy: AOS-CX switches use a " top-down " approach for QoS.

Global Trust: Setting qos trust dscp globally means that, by default, every port on the switch will look at the Layer 3 DSCP markings to determine queue priority.

Interface Override: You can override the global setting on a per-interface basis. If a specific device or service (like the video streaming service in this prompt) relies solely on Layer 2 CoS (802.1p) markings rather than DSCP, the switch will ignore those CoS markings under the global DSCP policy and place the traffic in a default (best-effort) queue.

LAG Configuration Logic: In the AOS-CX architecture, a LAG is a logical interface (interface lag 20).

Configuration parameters for the bundle (such as VLANs, ACLs, and QoS trust) should be applied to the logical LAG interface , not the individual physical member ports (1/1/20 and 2/1/20).

Once applied to the LAG, the settings are automatically inherited by all physical members.

Analyzing the Options:

Option D (Correct): By entering the interface lag 20 context and applying qos trust cos, you are instructing the switch to ignore the global DSCP setting for this specific bundle and instead trust the Layer 2 priority bits. This allows the video service to once again map correctly to the intended priority queues.

Option A: This is unnecessarily complex. Setting the physical member ports to qos trust none and then the LAG to cos is redundant because the LAG configuration overrides the physical port settings in this context.

Option B: qos trust dscp, cos is not a valid AOS-CX command. Unlike the older AOS-S (ProCurve) software which allowed a combined dscp-cos trust, AOS-CX requires you to choose a single trust type (DSCP, CoS, or None) per interface.

Option C: This applies the configuration to the physical ports only. In an AOS-CX VSF/LAG environment, this is considered a configuration error or " best practice " violation, as the logical LAG interface should hold the configuration.

When configuring OSPF on a point-to-point network type (typically a direct link between two routers), OSPF treats the link as a broadcast-less point-to-point segment.

This reduces unnecessary OSPF overhead by eliminating the need for:

DR/BDR elections (which generate LSA Type 2 advertisements for broadcast multi-access networks).

Thus, changing network type to point-to-point reduces the number of LSA Type-2 advertisements, which are used to describe the network segment in multi-access environments.

No impact on number of routes (LSA Type-3 is about inter-area routes).

The default is usually broadcast or point-to-multipoint depending on interface.

If the ISL between two VSX core switches is down and logs indicate that Core-2 has disabled its VSX LAG interfaces, it means Core-2 has disabled its VSX LAG interfaces, likely as a protective or failover mechanism.

Keepalive packets being dropped (Option B) may cause issues but logs specifically state interface disablement.

Both switches forwarding traffic (Option C) is unlikely if ISL is down.

Downstream switches inability to forward traffic (Option D) is a consequence, not the cause.