Examkin

Soru

Zorluk: OrtaSoftware-Defined Architectures: Overlay, Underlay, and Fabric

A network engineer is deploying an enterprise Software-Defined Access (SD-Access) fabric that uses Virtual Extensible LAN (VXLAN) for overlay data plane encapsulation across a Layer 3 underlay routed network. During testing, endpoints sending standard 1500-byte IP packets with the Don't Fragment (DF) bit set experience packet drops when traffic traverses the fabric. Which modification to the underlay network infrastructure resolves this issue?

  1. Increase the Maximum Transmission Unit (MTU) size on physical underlay interfaces to accommodate encapsulation overhead.Cevap
  2. B
    Enable Locator/ID Separation Protocol (LISP) on transit routers within the underlay to handle packet fragmentation.
  3. C
    Configure Port Address Translation (PAT) on Virtual Tunnel Endpoints (VTEPs) to compress outer IP header fields.
  4. D
    Convert access edge switch ports into 802.1Q trunks to strip inner headers prior to underlay forwarding.

Cevap

Increase the Maximum Transmission Unit (MTU) size on physical underlay interfaces to accommodate encapsulation overhead.
VXLAN overlay encapsulation adds 50 bytes of header overhead to standard frames. To ensure that 1500-byte payload packets marked with the Don't Fragment (DF) bit can pass through the underlay without being dropped, the physical underlay infrastructure must be configured with an increased MTU (typically 1550 bytes or higher).

Adım Adım Çözüm

1
Analyze the impact of overlay data plane encapsulation on packet size.
VXLAN encapsulation adds 50 bytes of overhead (Outer Ethernet + Outer IP + UDP + VXLAN headers) to original host frames.
When a 1500-byte payload frame is encapsulated by a VTEP, the total frame size exceeds the standard 1500-byte underlay MTU boundary.
2
Evaluate the behavior of packets with the Don't Fragment (DF) bit set.
Underlay routers drop packets exceeding their interface MTU because fragmentation is explicitly prohibited by the DF bit.
To prevent packet drops, the underlying physical transport network must support jumbo frames or an MTU size large enough (typically 1550-9000 bytes) to transport the full encapsulated packet without fragmentation.

Anahtar Kavram

Underlay MTU requirements for VXLAN overlay encapsulation
Bu soruyu puanla

Konular

Software-Defined Architectures: Overlay, Underlay, and Fabric

Bu konudan daha fazla soru