The event log showing PMK (Pairwise Master Key) and OKC (Opportunistic Key Caching) key add/update and delete operations is indicative of normal client behavior in a WLAN environment. These events are part of the standard process for maintaining client session security and do not necessarily indicate any issue.

When an SSID profile is configured with both primary and secondary gateway clusters, access points (APs) form IPsec tunnels to one of these clusters based on reachability and preemption logic.

How Aruba gateway cluster selection works:

The AP first attempts to connect to the primary gateway cluster.

If the primary cluster is unreachable, the AP establishes a tunnel with the secondary cluster.

Once both clusters are reachable again, the preemption setting determines whether APs should move back to the primary cluster or remain connected to the secondary.

Exact Extract (from Aruba AOS 10 Gateway and WLAN Deployment Guide):

“When both primary and secondary gateway clusters are configured on an SSID, access points distribute across both clusters depending on availability and preemption configuration. If preemption is disabled, access points that have joined the secondary cluster remain there even after the primary cluster becomes available, potentially leading to an even split across both clusters.”

“Preemption ensures APs automatically reconnect to the primary cluster when it is back online. If preemption is not enabled, APs stay attached to whichever cluster they joined first.”

This means that if preemption is not enabled, some APs that previously connected to the secondary cluster (during a temporary network or reachability issue) will remain there after recovery, resulting in a balanced or equal distribution between primary and secondary clusters.

Why the Other Options Are Incorrect:

A. The secondary gateway cluster is a heterogeneous cluster with four nodes:Cluster type (homogeneous or heterogeneous) does not cause APs to split evenly. Aruba does not recommend heterogeneous clustering.

“Cluster node homogeneity affects compatibility and performance, not AP distribution.”

B. The primary gateway cluster is a homogeneous cluster with four nodes:Cluster size or node count (homogeneous or heterogeneous) does not influence the AP split behavior.

“Cluster node count determines capacity, not tunnel distribution.”

C. The primary and secondary gateway clusters are up, and cluster preemption is enabled:With preemption enabled, APs connected to the secondary cluster automatically move back to the primary once it’s reachable — eliminating an even split.

“Preemption ensures all APs return to the primary cluster, maintaining centralized control.”

References of HPE Aruba Networking Switching Documents or Study Guide:

ArubaOS 10 WLAN and Gateway Deployment Guide – “AP tunnel distribution behavior with primary/secondary gateway clusters and preemption settings.”

Aruba High Availability and Redundancy Best Practices Guide – “Impact of preemption on AP failover and cluster load balancing.”

Aruba Mobility Gateway Configuration Guide – “Gateway clustering, AP tunnel association logic, and preemption operation.”

Aruba Campus Wireless Design Fundamentals – “Cluster redundancy, AP tunnel behavior, and balanced AP distribution across clusters.”

Comprehensive and Detailed Explanation (Verified Extract from HPE Aruba Networking Switching Documentation)

VOQ (Virtual Output Queuing) is a hardware-based queuing mechanism used in the ArubaOS-CX architecture to prevent head-of-line blocking and minimize packet drops in high-throughput environments.

How VOQ Works:

Each ingress port maintains a separate queue for every egress port in the system.

When a packet arrives, it is placed in the ingress buffer corresponding to its destination egress port.

This structure ensures that traffic destined for one congested egress port does not block packets heading to other ports.

This architecture is critical in high-speed modular switches and aggregation cores (such as the Aruba 8400 and 10000 Series), allowing the fabric interconnect to forward traffic efficiently without dropping packets due to port congestion.

ArubaOS-CX Technical Extract:

“Virtual Output Queuing (VOQ) provides per-egress-port queuing at ingress buffers, preventing head-of-line blocking and ensuring high throughput across the switch fabric. Each ingress queue corresponds to a specific egress port, allowing packets to be transmitted as soon as the egress port becomes available.”

Option Analysis:

A. Incorrect – Refers to priority marking (QoS), not VOQ operation.

B. Correct – VOQ provides ingress buffers with queues for each egress port, reducing dropped packets and head-of-line blocking.

C. Incorrect – VOQ is not related to LACP or VSX link aggregation.

D. Incorrect – VOQ does not dynamically allocate egress buffer space; it segregates ingress queues per egress destination.

Final Verified Answer: B

Reference Sources (HPE Aruba Official Materials):

Aruba AOS-CX Technical Architecture Overview – Virtual Output Queuing (VOQ)

Aruba 8400/10000 Series Switches Hardware and Performance Guide

Aruba Certified Switching Expert (ACSE) Study Guide – Switch Fabric and Queuing Mechanisms

Comprehensive and Detailed Explanation From Exact Extract of HPE Aruba Networking Switching:

When an AOS-10 gateway is onboarded into Aruba Central using the Full-Setup method, a local admin password is defined during the setup wizard on the gateway itself. Later, when the gateway joins an existing Aruba Central group, the group-level configuration (which includes the admin password defined for that group) is automatically pushed down to all devices in that group for configuration consistency.

However, if the password defined during full-setup is different from the admin password defined in the Aruba Central group, the synchronization process can cause a mismatch between the local device password and the one expected by Central. This mismatch prevents remote console login from working properly because Aruba Central attempts to authenticate to the gateway using the group-level admin credentials, not the local credentials from full-setup.

Exact Extract from HPE Aruba Networking Switching and Aruba Central Configuration Documents:

“During onboarding, the admin password configured at the group level in Aruba Central is applied to all devices in the group. If a device is added using full-setup with a different password, it may fail Central-initiated authentication functions such as remote console.”

“When gateways are provisioned using the full-setup workflow, the local administrator password must match the group-level administrator credentials in Aruba Central to allow remote console and CLI access through Central.”

Therefore, the issue arises because the full-setup password for the gateway does not match the group admin password defined in Aruba Central, resulting in the ‘incorrect password’ error when attempting to access the gateway remotely through Central.

Why the Other Options Are Incorrect:

A. The full-setup admin password is valid for remote access; there is no separate configuration option that “allows” or “disallows” remote console use.

“Remote console access uses the same admin account configured for device login; there is no additional enablement required.”

B. Aruba Central admin passwords do not expire by default. Group-level admin credentials are persistent configuration items, not time-based credentials.

“Local and group administrator passwords are static until manually changed.”

C. There is no “global Aruba Central admin password” used to authenticate to devices; authentication is performed using per-group or per-device credentials configured in Central.

“Each Aruba Central group maintains its own admin credentials that are propagated to member devices; there is no single global password for all groups.”

References of HPE Aruba Networking Switching Documents or Study Guide:

ArubaOS 10.5.0 Gateway Deployment and Configuration Guide – “Onboarding using Full Setup” and “Group-Level Configuration Synchronization.”

Aruba Central Device Management Guide – “Group Admin Credentials and Remote Console Access.”

Aruba AOS 10 Campus Gateway Installation and Setup Guide – “Matching Group Admin Passwords for Central-Managed Devices.”

The provided output is from the command:

(MC2) #show auth-tracebuf mac

This command traces the authentication exchange between the access point (or mobility controller) and the RADIUS server for a specific client. The trace provides insight into the 802.1X authentication sequence and RADIUS responses.

From the exhibit:

EAPOL (Extensible Authentication Protocol over LAN) Messages Observed:

eap-id-req

eap-id-resp

eap-req

eap-resp

eap-success

These messages clearly indicate that an 802.1X (EAP-based) authentication took place. MAC authentication (MAB) or WebAuth would not include multiple EAP identity and response messages.

RADIUS Messages:

rad-req, rad-resp, rad-accept from /RADIUS1

The presence of rad-accept indicates successful authentication.

Exact extract from ArubaOS (AOS-S/AOS 10 WLAN Authentication Guide):

“When the trace output shows EAP identity requests, EAP responses, and a RADIUS Access-Accept message, the authentication method in use is 802.1X (EAP-based user authentication). The presence of EAP-Success following the Access-Accept confirms successful 802.1X authentication.”

Follow-on WPA2 Key Exchange:

Lines show wpa2-key1, wpa2-key2, wpa2-key3, and wpa2-key4.

This sequence occurs after 802.1X authentication completes and is used to establish encryption keys for a WPA2 Enterprise session.

Exact extract from Aruba WLAN Troubleshooting Guide:

“After successful 802.1X authentication (EAP-Success), the controller exchanges four WPA2 keys with the station to derive the session keys used for data encryption. This confirms WPA2-Enterprise with 802.1X was used.”

No Indication of MAC or WebAuth:

MAC authentication would show mac-auth or macauth messages instead of eap-id-req/resp.

WebAuth involves HTTP-based redirection and is not visible in auth-tracebuf as EAP transactions.

Exact extract:

“MAC authentication shows ‘macauth start’ and ‘macauth accept’ entries, not EAPOL frames. WebAuth authentication uses a web redirect and does not appear as EAP frames in the trace buffer.”

Therefore, the trace confirms a WPA2-Enterprise 802.1X user authentication, where the user’s credentials were validated by the RADIUS server, followed by the WPA2 key handshake.

Why the Other Options Are Incorrect:

A. MAC authentication:Would show MAC-based request/response entries (macauth), not eap-id-req/resp.

C. WEBauth authentication:WebAuth occurs over HTTP/HTTPS and does not involve EAP messages; thus, no eap-id or eap-success would be seen.

D. 802.1X machine authentication:Machine authentication occurs before user logon and is typically identified in logs by a computer account (e.g., host/computername$). Here, the username and context indicate a user-level session.

References of HPE Aruba Networking Switching Documents or Study Guide:

ArubaOS 8/10 WLAN Authentication and Security Configuration Guide – “802.1X EAP Authentication and Trace Analysis.”

Aruba WLAN Troubleshooting Guide – “Using show auth-tracebuf to validate EAP authentication.”

Aruba Campus Wireless Design Fundamentals – “Understanding WPA2-Enterprise authentication flow (EAPOL, RADIUS, WPA2 4-Way Handshake).”

Aruba Access Security and AAA Implementation Guide – “Distinguishing between MAC, WebAuth, and 802.1X authentication in debug outputs.”

The CLI output shown is from the Aruba CX 6300 running AOS-CX, displaying the routing table in an EVPN-VXLAN fabric environment.

Key details from the output:

Prefix Nexthop Interface Origin/Type Distance/Metric

10.203.1.0/24 - vlan203 C [0/0]

10.203.1.1/32 - vlan203 L [0/0]

10.203.1.100/32 172.21.11.2 - B/EV [200/0]

172.21.11.4/32 172.21.11.2 - B/EV [200/0]

172.21.11.5/32 - loopback3 L [0/0]

From this, we can interpret the following:

Routes marked as B/EV originate from BGP EVPN, meaning they are advertised and learned over the VXLAN fabric.

The next hop 172.21.11.2 indicates that these routes are learned from another fabric device with loopback address 172.21.11.2.

The route 10.203.1.100/32 is a host route (specific endpoint) reachable via that remote switch.

According to the Aruba CX EVPN-VXLAN Fabric Deployment Guide:

“In a VXLAN fabric, host routes (/32) are dynamically advertised using EVPN Type 2 routes.

These routes include MAC/IP bindings of endpoints connected to remote VTEPs (loopbacks).

The next-hop address in the routing table corresponds to the VTEP IP (loopback address) of the remote switch where the client resides.”

Thus, the presence of a /32 route (10.203.1.100/32) with next hop 172.21.11.2 indicates that this wired client resides behind another CX 6300 fabric node whose VTEP address is 172.21.11.2.

Option Analysis:

A. Correct – The /32 route confirms that 10.203.1.100 is reachable via remote CX at 172.21.11.2 (remote VTEP).

B. Incorrect – The RD information isn’t shown here; this statement cannot be validated and contradicts visible EVPN entries.

C. Incorrect – The route is properly advertised and reachable via EVPN; no indication of advertisement failure.

D. Incorrect – Overlay loopbacks (172.21.11.x) are advertised as /32 host routes, not /24 subnets.

Final Verified Answer: A

Reference Sources (HPE Aruba Official Materials):

Aruba AOS-CX EVPN-VXLAN Fabric Deployment and Configuration Guide

Aruba CX 6300 Routing and BGP Configuration Guide

Aruba Certified Switching Professional (ACSP) Study Guide – EVPN-VXLAN Route Interpretation

When configuring Virtual Switching Extension (VSX) in a campus topology for link aggregation across two aggregation switches, it is important to synchronize Multi-Chassis Link Aggregation Group (MC-LAG) interfaces. The command "vsx-sync mclag-interfaces" ensures that the state and configuration of MC-LAG interfaces are synchronized between the two VSX-linked switches, providing consistent link aggregation and preventing any loops or mismatched configurations that might occur if the interfaces were not in sync.