CDCP Network Infrastructure and Connectivity 5 ā Questions and Answers
Question 1: What is the maximum transmission unit (MTU) typically required when using VXLAN encapsulation to avoid fragmentation of standard 1500-byte Ethernet frames?
- 1500 bytes
- 1518 bytes
- 9000 bytes (Correct answer)
- 4096 bytes
Correct answer: 9000 bytes
VXLAN adds 50 bytes of overhead; to carry a full 1500-byte payload without fragmentation, jumbo frames with an MTU of at least 1550 bytes are needed, and 9000-byte jumbo frames are the standard data center practice.
Question 2: In BGP-based data center fabrics, what is the role of the 'route reflector'?
- It mirrors all network traffic for inspection
- It reduces full-mesh iBGP peering requirements by redistributing routes on behalf of peers (Correct answer)
- It translates between IPv4 and IPv6 routing domains
- It performs NAT for outbound data center traffic
Correct answer: It reduces full-mesh iBGP peering requirements by redistributing routes on behalf of peers
A BGP route reflector eliminates the need for every iBGP speaker to peer with every other, reducing O(nĀ²) peering sessions to a hub-and-spoke model.
Question 3: Which technology allows a data center to present a single logical switch across multiple physical switches, simplifying topology and eliminating spanning tree?
- VPC (Virtual Port Channel)
- VSS (Virtual Switching System) / MC-LAG (Correct answer)
- TRILL
- FCoE
Correct answer: VSS (Virtual Switching System) / MC-LAG
Multi-Chassis Link Aggregation (MC-LAG) technologies like VSS or vPC present multiple physical switches as a single logical device, enabling active-active uplinks without spanning tree loops.
Question 4: A colocation data center customer requests a cross-connect. What does a cross-connect provide?
- A virtualized network segment between two VMs
- A physical cable connection between two customer cages or a customer and a carrier (Correct answer)
- A logical VPN tunnel between two remote sites
- An out-of-band management link to network devices
Correct answer: A physical cable connection between two customer cages or a customer and a carrier
A cross-connect is a dedicated physical cable (copper or fiber) installed by the colocation facility to directly connect two parties within the same data center without traversing public networks.
Question 5: What is the primary purpose of an out-of-band (OOB) management network in a data center?
- To carry production application traffic at lower latency
- To provide device access for management and recovery independent of the production network (Correct answer)
- To extend VLANs between geographically distributed data centers
- To connect the data center to the internet via a secondary ISP
Correct answer: To provide device access for management and recovery independent of the production network
An OOB management network is physically separate from production traffic paths, allowing administrators to access, configure, or recover devices even when the in-band network is down.
Question 6: Which type of optical transceiver form factor is most commonly used in high-density 100GbE data center switch ports today?
- SFP
- QSFP28 (Correct answer)
- XFP
- CFP2
Correct answer: QSFP28
QSFP28 (Quad Small Form-factor Pluggable 28) supports 100GbE in a compact form factor and is the dominant standard for 100G switch ports in modern data centers.
Question 7: A network engineer needs to segment traffic in a data center between different departments without deploying separate physical switches. Which technology is the standard solution?
- Subnetting only
- VLANs (Virtual LANs per IEEE 802.1Q) (Correct answer)
- MPLS L3VPN
- SD-WAN
Correct answer: VLANs (Virtual LANs per IEEE 802.1Q)
VLANs per IEEE 802.1Q logically segment a single physical switch into multiple broadcast domains, isolating traffic between departments without additional hardware.
CDCP Network Infrastructure and Connectivity 5
What is the maximum transmission unit (MTU) typically required when using VXLAN encapsulation to avoid fragmentation of standard 1500-byte Ethernet frames?