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

Comprehensive and Detailed In-Depth Explanation:

InOSPFv3, theAS-external-LSA (Type 5 LSA)is the only LSA type that can beflooded throughout the entire Autonomous System (AS). It is used to advertise external routes (routes redistributed from other routing protocols or static routes) into the OSPF domain.

B. Intra-Area-Prefix-LSA (Type 9):Used to advertise IPv6 prefixes within an OSPF area, not across the AS.

C. Link-LSA (Type 8):Advertises link-local addresses and options, only within the local link, not the entire AS.

D. Inter-Area-Prefix-LSA (Type 3 or Type 4):Advertises prefixes between OSPF areas but not throughout the entire AS.

OnlyAS-external-LSAs (Type 5)can be propagated across the whole OSPF AS, making them essential for exchanging routes learned from other routing protocols.

Comprehensive and Detailed In-Depth Explanation:

In the Label Distribution Protocol (LDP) session establishment process, theInitialization messageis sent by the initiator to propose parameters for the session. If the responder finds that the proposed parameters are not acceptable, it responds with anError Notification Message. This message indicates that the session could not be established due to incompatible or incorrect parameters.

TheError Notification Messagetypically includes details about why the session could not be established, such as parameter mismatch or unsupported features. If the parameters are acceptable, the responder would instead reply with aKeepalive Messageto maintain the session.

BGP routing policiesallow administrators to:

Control incoming and outgoing routes.

Filter routes based onprefix, AS-PATH, communities, MED, next hop, etc.

Apply route maps, prefix lists, or filter policies during:

Route advertisement

Route reception

Route import/export into local RIB or VPN instance

This is a fundamental capability of BGP and is widely used in production environments for traffic engineering, route filtering, and policy-based routing.

Correct answer: A. TRUE

Understanding SR-MPLS Prefix and Adjacency Segments

🔹What Are Prefix Segments?

Globally uniquelabels assigned to network prefixes.

Advertised viaIGP (OSPF, IS-IS) with SRGB (Segment Routing Global Block).

🔹What Are Adjacency Segments?

Locally significant labelsassigned to direct router adjacencies.

Not globally visible—only used within a local router’sLFIB (Label Forwarding Information Base).

Why is the Answer FALSE?

❌Prefix Segments are globally unique, but Adjacency Segments are only locally significant.

❌Adjacency Segments are not distributed globally through IGP.

✅Only Prefix Segments use globally advertised SRGB labels.

Real-World Application:

Segment Routing Traffic Engineering (SR-TE):Usesprefix segments for global routingandadjacency segments for local path steering.

5G Core Networks:UsesSR-MPLS with Prefix SIDs for scalable path selection.

✅Reference:Huawei HCIE-Datacom Guide – SR-MPLS Prefix & Adjacency Segments

InMPLS Traffic Engineering (TE),Label Switched Paths (LSPs)can be established:

Statically: Manual configuration.

Dynamically: Typically viaRSVP-TE.

Protocol roles:

RSVP-TE:Used to dynamically establish and signal TE LSPs→✅

OSPF / IS-IS: Act asIGP protocolsand provide TE-related link-state information (like bandwidth) butdo not establish LSPs themselves→❌

BGP: Used forroute advertisement, not forLSP setupin MPLS TE →❌

Correct answers: A, C, D

VXLAN Inter-Subnet Routing with Symmetric IRB

VXLAN supportsinter-subnet routingusingIntegrated Routing and Bridging (IRB). Insymmetric IRB, both ingress and egress VTEPs performLayer 3 forwardingto ensure efficient packet forwarding across subnets.

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

Insymmetric IRB, bothingress and egress VTEPs perform Layer 3 lookup and forwarding.

The ingressroutes packets before encapsulating them in VXLAN, and the egressperforms 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 forinter-subnet routingbetween VXLAN segments.

Understanding EVPN (Ethernet VPN) Label Allocation and ARP Handling

🔹What Happens in This Scenario?

1️⃣CE1 (192.168.1.1) sends an ARP request to discover the MAC address of CE2 (192.168.1.2).

2️⃣PE1 receives the ARP request and needs to forward it over the EVPN fabric.

3️⃣To send the broadcast ARP request across the EVPN network, PE1 forwards the packet to PE4 using BUM (Broadcast, Unknown unicast, and Multicast) forwarding.

4️⃣PE4, as the Designated Forwarder (DF), forwards the ARP request to CE2.

Role of Labels in EVPN VXLAN/MPLS Networks

🔹EVPN uses BGP to distribute MAC/IP reachability information using different route types.

✅EVPN Type 2 Route (MAC/IP Advertisement Route):

Used forMAC-to-IP address mappingannouncements.

Ensuresremote VTEPs (PE routers) learn MAC-to-IP bindingsdynamically.

✅EVPN Type 3 Route (Inclusive Multicast Route):

Used forBUM traffic (Broadcast, Unknown Unicast, Multicast).

Assigns a multicast label (e.g., 201) to be used for forwarding broadcast packets like ARP requests.

🔹In this case:

Thelabel 201is used forBUM traffic forwarding.

BUM traffic is handled using an EVPN Type 3 route.

Why is the Answer 3?

✅EVPN Type 3 routes carry labels for BUM traffic, which includes ARP requests.

✅Label 201 is used for multicast distribution, which is managed by Type 3 routes.

Real-World Application:

VXLAN Data Centers:UsesEVPN Type 3 routes to control BUM traffic efficiently.

Campus Networks:Preventsunnecessary flooding of ARP requests across VXLAN domains.

✅Reference:Huawei HCIE-Datacom Guide – EVPN BGP Route Types and Multicast Labeling