Pass the HP Aruba Certified Switching Expert HPE7-A08 Questions and answers with CertsForce

To enable Layer 3 multicast functionality on an AOS-CX switch, it is essential to understand the roles of different protocols and where they are applied in the hierarchy of the switch configuration.

L3 vs. L2 Multicast:

IGMP (Internet Group Management Protocol): This is a Layer 3 protocol used by hosts to report their multicast group memberships to adjacent routers. It is configured on a Layer 3 interface , such as an SVI (Switch Virtual Interface) or a routed port.

IGMP Snooping: This is a Layer 2 optimization feature. It allows a switch to " listen in " on IGMP conversations between hosts and routers to constrain multicast traffic to only those ports that have requested it, preventing the traffic from flooding the entire VLAN.

Enabling L3 Multicast Locally: When the " core switch " acts as the default gateway for multicast receivers, it must be able to process membership reports from those receivers. By enabling IGMP on the SVI (e.g., interface vlan 100), the switch begins listening for IGMP Join/Leave messages from clients on that subnet. This is a prerequisite for the switch to populate its multicast routing table and, when combined with a routing protocol like PIM (Protocol Independent Multicast) , forward traffic from a source to those local receivers.

Analysis of Options:

Option A (Correct): IGMP must be enabled on the SVI so the switch can function as a multicast-aware gateway for that specific subnet.

Option B: In AOS-CX syntax, you do not configure " IGMP " under the L2 vlan [ID] context; it is an L3 function.

Option C: Enabling IGMP-snooping on a VLAN only manages the L2 delivery of traffic; it does not enable L3 routing or the processing of multicast packets across different subnets.

Option D: While IGMP-snooping is often used in conjunction with L3 multicast, it is technically a VLAN-level configuration, not a property of the SVI itself.

Key CLI Commands:

To fully enable this, a professional would typically use:

Bash

router multicast

routing

!

interface vlan 100

ip igmp

ip pim-sm

To avoid split-brain scenarios in VSF stacks, the VSL split-detect mgrep command is used to enable multicast group detection over the Virtual Switching Link (VSL). This helps detect when the stack links are down or partitioned, triggering appropriate failover or shutdown mechanisms.

Options like vsf start-auto-stacking, vsf secondary-member 2, or vsf conductor-member 2 are related to stack initialization and member roles but do not address split-brain detection directly.

Hence, enabling split-detect with mgrep is the best practice for VSF stack stability.

The issue is VMware vMotion traffic on VLAN 3903 failing, while other VLANs work normally. vMotion traffic requires support for larger frame sizes (jumbo frames) because vMotion packets are large and benefit from increased MTU to improve performance and reduce fragmentation.

Configuring jumbo frames on VLAN 3903 ensures that frames on this VLAN can use an MTU larger than the default 1500 bytes.

Configuring jumbo on the interface alone may not be sufficient if the VLAN itself is not set to support jumbo frames.

Setting MTU on VLAN or interface might not work unless jumbo frames are enabled.

This exhibit highlights a critical operational requirement for Virtual Switching Extension (VSX) : Version Consistency .

Analyzing the Exhibit: * The Local Software Version is GL.10.09.0010.

The Peer (sw-agg2) Software Version is GL.10.11.1021.

The Config Sync Status explicitly reports: sw_image_version_mismatch_error.

The Impact of Software Mismatch: The VSX configuration synchronization engine ( vsx-sync ) requires that both the primary and secondary switches run the exact same version of AOS-CX. When a mismatch is detected, the synchronization of configuration (VLANs, LAGs, etc.) is immediately halted to prevent database corruption or unpredictable behavior.

Incompatible State: While the data plane (traffic forwarding) typically continues to function using the last known good configuration, the control plane " cluster " is effectively in an incompatible mode for management. You cannot make configuration changes on the Primary and expect them to push to the Secondary until the versions are aligned.

Evaluating Other Options:

Option A: Incorrect. The mismatch_error halts all config sync, regardless of whether the specific command exists in both versions.

Option C: A " Live Upgrade " (VSX Orchestration) requires both switches to have access to the same target image and for the sync engine to be healthy. You cannot live upgrade when the sync engine is already in an error state.

Option D: VSX is a distributed forwarding architecture. It does not " forward all traffic " to the primary. Traffic is balanced across MC-LAG links unless a physical failure occurs.

https://arubanetworking.hpe.com/techdocs/AOS-CX/10.16/HTML/high_availability/Content/Chp_BFD/cnf-bfd-bgp-10.htm

In a VSX cluster, certain configurations such as DHCP relay need to be synchronized between both nodes. To sync DHCP relay configuration from the primary to the secondary, the command:

vsx-sync dhcp-relay

must be added under the VSX configuration on the primary switch. This ensures that DHCP relay settings are pushed to the secondary member automatically.

Adding vsx-sync ip-helper relates to IP helper addresses, not DHCP relay specifically.

Adding the sync command on the secondary has no effect as synchronization originates from primary.

To resolve vMotion connectivity issues on an Aruba AOS-CX 8320 , we must ensure the network infrastructure supports Jumbo Frames end-to-end.

MTU and vMotion Requirements: VMware vMotion is highly sensitive to the Maximum Transmission Unit (MTU). For optimal performance and reliability, a 9000-byte MTU is standard. If any switch port in the path is left at the default 1500-byte MTU , vMotion operations will typically time out or fail, even if standard small-packet traffic (like a basic ping) works.

AOS-CX Configuration Syntax: In the AOS-CX operating system, Jumbo frame support is enabled by modifying the MTU at the interface level.

The standard command is mtu 9198.

The value 9198 is used because it accounts for the 9000-byte payload plus L2 headers and tagging overhead.

Unlike the older AOS-S (ProCurve) software, AOS-CX does not use the jumbo command; it uses the mtu command under the physical interface context.

Analyzing the Exhibits:

The Configuration: The exhibit for interface 1/1/35 shows a standard trunk configuration but no MTU command . This confirms the port is operating at the default 1500-byte limit.

The Statistics: The show interface extended output shows TX Jumbos: 6666. This indicates that jumbo packets have been sent, but in a troubleshooting context, this may represent previous stats or the switch counting oversized frames before dropping them or failing to receive them from the server.

Why Option B is the Correct Fix: Even if " large " pings (e.g., 2000 bytes) work due to fragmentation or " baby giant " tolerances, the specific high-throughput requirements of vMotion necessitate that the physical transport layer (interface 1/1/35) be explicitly configured to handle the full 9000-byte frame size using the mtu 9198 command.

Addressing the SVI (Option A): While an SVI (interface vlan 3903) also has an MTU, the physical port is the primary gatekeeper for Layer 2 traffic. If the physical port is set to 1500, no jumbo frame will ever reach the SVI or be switched to another port on that VLAN.

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.

To prevent the campus core from seeing the data center core as the root bridge in a spanning tree topology (which can cause suboptimal paths or loops), Root Guard should be applied on the campus-to-data center core link. Root Guard enforces root bridge placement by blocking any superior BPDU from a downstream switch, maintaining the intended root bridge location.

BPDU filter blocks BPDUs entirely, which can cause problems.

Admin edge and BPDU guard are related to edge port protection, not root placement control.

To find which changes were made on an HPE Aruba CX switch from the GUI, the correct command is:

show checkpoint diff — this compares the running configuration with stored saved-config revisions.

Using " saved-config revisions " as the comparison base allows the GUI to show what has changed since the last saved configuration.

Other options mix checkpoint and saved-config terminology incorrectly.