H12-891_V1.0 Exam Dumps : HCIE-Datacom V1.0

VXLAN Inter-Subnet Routing with Symmetric IRB

VXLAN supports inter-subnet routing using Integrated Routing and Bridging (IRB). In symmetric IRB, both ingress and egress VTEPs perform Layer 3 forwarding to ensure efficient packet forwarding across subnets.

✅ A. Both the ingress VTEP and egress VTEP forward packets based on the Layer 3 forwarding table.

In symmetric IRB, both ingress and egress VTEPs perform Layer 3 lookup and forwarding.

The ingress routes packets before encapsulating them in VXLAN, and the egress performs another Layer 3 lookup to determine final delivery.

✅ D. When VTEPs forward inter-subnet user communication packets, the VNI carried in the VXLAN header is the L3VNI.

L3VNI (Layer 3 VXLAN Network Identifier) is used for inter-subnet routing between VXLAN segments.

FEC (Forwarding Equivalence Class) in MPLS is a group of packets that are forwarded in the same manner. MPLS can classify packets into FECs based on factors such as:

Destination IP address

Source address

CoS (Class of Service)

Application type

However, Fragment Offset, which is part of the IP header used for IP fragmentation, is not used in FEC classification. Fragment offset is more relevant to how IP packets are reconstructed and not suitable or used as a classification standard for forwarding decisions in MPLS.

Exact Extract - Huawei HCIE-Datacom V1.0 MPLS Chapter:

“FEC classification may be based on various parameters including destination address, source address, and even CoS values. However, fragment offset is not used as an FEC criterion, as MPLS forwarding occurs before IP reassembly.”

OSPFv3 (used for IPv6) uses IPv6 multicast addresses for communication between routers:

FF02::5 — All OSPF routers.

FF02::6 — All OSPF Designated Routers (DRs) and Backup Designated Routers (BDRs).

FF08::x — These are used for organization-local scope, which is not applicable to standard OSPFv3 operation.

Therefore:

C. All OSPF routers use FF02::5 — Correct

D. The DR uses FF02::6 — Correct

A and B (FF08::x) — Incorrect. These addresses are not used by OSPFv3 in this context.

Correct answers: C and D