ACSP AOS-CX VSF and VSX 5 — Questions and Answers
Question 1: When a downstream access switch connects to a VSX pair via MCLAG, which spanning tree port state does the MCLAG port-channel typically operate in?
- Blocking on the Secondary peer and Forwarding on the Primary
- Forwarding on both peers simultaneously (Correct answer)
- Listening on both peers until STP converges
- Discarding on the Primary and Forwarding on the Secondary
Correct answer: Forwarding on both peers simultaneously
MCLAG presents a single logical LAG to STP so both peers' physical links remain in Forwarding state simultaneously, eliminating blocked uplinks.
Question 2: What is a key operational difference between VSF and VSX when one member/peer loses power?
- VSF continues forwarding on surviving members; VSX shuts down all ports on the remaining peer
- VSF reconverges as remaining members take over; VSX Secondary shuts MCLAG ports in split-brain only when ISL also fails (Correct answer)
- Both VSF and VSX enter split-brain mode on any single failure
- VSX reconverges instantly; VSF requires manual recovery
Correct answer: VSF reconverges as remaining members take over; VSX Secondary shuts MCLAG ports in split-brain only when ISL also fails
In VSF a member loss triggers stack reconvergence but traffic continues; in VSX, losing a peer only causes MCLAG shutdown if both ISL and keepalive are also gone.
Question 3: In AOS-CX VSX, which protocol is used by the keepalive link to verify peer liveness?
- BFD (Bidirectional Forwarding Detection)
- UDP-based VSX heartbeat messages (Correct answer)
- ICMP echo requests
- LACP PDUs
Correct answer: UDP-based VSX heartbeat messages
VSX uses proprietary UDP-based heartbeat messages over the keepalive link to determine whether the peer is alive, independent of the ISL.
Question 4: Which AOS-CX VSF command allows an administrator to manually trigger a failover and promote the Standby to Conductor?
- vsf failover (Correct answer)
- vsf move-role standby conductor
- redundancy switchover
- vsf promote member 2
Correct answer: vsf failover
The 'vsf failover' command initiates a graceful failover, promoting the Standby member to Conductor and demoting the current Conductor.
Question 5: When configuring VSX on AOS-CX switches, on which interface type is the 'vsx peer-link' designation applied?
- Physical routed port
- VLAN interface (SVI)
- Port-channel (LAG) interface (Correct answer)
- Loopback interface
Correct answer: Port-channel (LAG) interface
The VSX ISL must be a port-channel (LAG) interface to provide the bandwidth and redundancy required; 'vsx peer-link' is configured on the port-channel.
Question 6: What is the purpose of the 'vsx-sync' configuration on an AOS-CX VSX switch?
- It forces both peers to share a single management session
- It specifies which protocol state (e.g., VLANs, OSPF, ACLs) is synchronized across the ISL (Correct answer)
- It sets the ISL keepalive interval
- It defines the MCLAG system-MAC address
Correct answer: It specifies which protocol state (e.g., VLANs, OSPF, ACLs) is synchronized across the ISL
The 'vsx-sync' stanza lists the specific protocol and configuration domains (VLANs, ACLs, OSPF, etc.) that should be synchronized between VSX peers over the ISL.
Question 7: Which statement is TRUE about VSF member IDs in AOS-CX?
- Member IDs are assigned dynamically by LLDP negotiation each boot
- Member IDs are statically configured and persist across reboots (Correct answer)
- The conductor always holds member ID 0
- Member IDs reset to sequential order after any topology change
Correct answer: Member IDs are statically configured and persist across reboots
VSF member IDs are statically configured by the administrator and stored in the switch's local configuration, persisting across reboots to maintain stable port numbering.
ACSP AOS-CX VSF and VSX 5
When a downstream access switch connects to a VSX pair via MCLAG, which spanning tree port state does the MCLAG port-channel typically operate in?