ACSP EVPN-VXLAN and Network Virtualization 1 — Questions and Answers
Question 1: What does VXLAN stand for?
- Virtual Extended Local Area Network
- Virtual Extensible Local Area Network (Correct answer)
- Variable Exchange LAN Architecture Network
- Virtualized External Link Access Node
Correct answer: Virtual Extensible Local Area Network
VXLAN stands for Virtual Extensible Local Area Network, a network virtualization technology that encapsulates Layer 2 frames within UDP packets to extend Layer 2 domains over Layer 3 infrastructure.
Question 2: What UDP destination port does VXLAN use by default for encapsulation, as standardized by IANA?
- 4789 (Correct answer)
- 8472
- 6081
- 1194
Correct answer: 4789
VXLAN uses UDP destination port 4789, as standardized by IANA in RFC 7348, ensuring interoperability across vendor implementations.
Question 3: What is the primary role of a VTEP (VXLAN Tunnel Endpoint) in a VXLAN overlay network?
- To provide DHCP services to overlay tenants
- To encapsulate and decapsulate VXLAN packets at the network edge (Correct answer)
- To advertise BGP routes to external peers only
- To terminate SSL/TLS tunnels for management traffic
Correct answer: To encapsulate and decapsulate VXLAN packets at the network edge
A VTEP encapsulates outgoing Layer 2 frames into VXLAN/UDP packets and decapsulates incoming VXLAN packets back to Layer 2, sitting at the boundary between overlay and underlay.
Question 4: What is a VNI (VXLAN Network Identifier) and how many unique values does it support?
- A 12-bit VLAN-like tag supporting up to 4,096 segments
- A 24-bit identifier supporting up to ~16 million unique tenant segments (Correct answer)
- A 32-bit identifier supporting up to ~4 billion segments
- A 16-bit identifier supporting up to ~65,536 segments
Correct answer: A 24-bit identifier supporting up to ~16 million unique tenant segments
A VNI is a 24-bit field that uniquely identifies a VXLAN segment, providing approximately 16 million unique tenant network identifiers versus only 4,096 VLANs.
Question 5: In EVPN-VXLAN, which BGP address family is used to distribute MAC and IP reachability information between VTEPs?
- IPv4 Unicast (AFI 1, SAFI 1)
- L2VPN EVPN (AFI 25, SAFI 70) (Correct answer)
- IPv6 Unicast (AFI 2, SAFI 1)
- VPNv4 (AFI 1, SAFI 128)
Correct answer: L2VPN EVPN (AFI 25, SAFI 70)
EVPN uses the L2VPN EVPN address family (AFI 25, SAFI 70) to distribute MAC/IP reachability, multicast group info, and other overlay control-plane data via BGP.
Question 6: What is the primary purpose of the underlay network in a VXLAN fabric deployment?
- To carry encapsulated VXLAN packets between VTEPs using IP routing (Correct answer)
- To provide out-of-band management access for fabric switches
- To handle raw multicast traffic for all tenant VLANs
- To enforce security policies between VRFs without routing
Correct answer: To carry encapsulated VXLAN packets between VTEPs using IP routing
The underlay is the routed IP network providing connectivity between VTEPs, enabling VXLAN-encapsulated overlay packets to traverse the physical infrastructure.
Question 7: On Aruba AOS-CX, which interface type is typically configured as the VTEP source interface for VXLAN tunnels?
- The management (mgmt) interface
- A loopback interface (Correct answer)
- The SVI of the native VLAN
- The OOBM (Out-of-Band Management) interface
Correct answer: A loopback interface
A loopback interface is used as the VTEP source because it is always logically up, stable, and reachable via multiple equal-cost paths in the underlay for redundancy.
ACSP EVPN-VXLAN and Network Virtualization 1
What does VXLAN stand for?