H12-821_V1.0 Exam Dumps - HCIP-Datacom-Core Technology V1.0

The Forwarding Information Base (FIB) is derived from the router's routing table and contains the exact forwarding entries used to route packets. It directly guides packet forwarding decisions by matching incoming packets with the correct output interface or next-hop address ​.

Understanding the LSDB and Level-2 DIS Election in IS-IS:

In IS-IS, the Designated Intermediate System (DIS) is elected for both Level-1 and Level-2 on broadcast networks to manage the link-state database (LSDB) and reduce the number of LSAs exchanged.

The election of the DIS is based on the highest priority. If the priority is the same, the router with the highest System ID becomes the DIS.

In an OSPF broadcast or NBMA network with at least two routers, one router must act as the DR (Designated Router), and another as the BDR (Backup Designated Router) to ensure efficient communication and reduce the number of adjacencies. This is a requirement for OSPF operation in such network types ​.

For single-hop BFD (Bidirectional Forwarding Detection), the configuration must include the local and remote discriminators to uniquely identify the session endpoints. Additionally, enabling BFD globally is a prerequisite for initiating BFD sessions. Configuring multicast IP addresses is unnecessary for single-hop BFD, as it operates over direct links. Huawei's configuration guidelines specify these requirements to ensure effective deployment and operation of BFD​​.

ï‚· Understanding BFD (Bidirectional Forwarding Detection):

BFD is a protocol used to detect link faults quickly between two routers.

Single-hop BFD operates on directly connected links and is commonly used for fast fault detection in routing protocols like OSPF and BGP.

High-availability Stateful Backup (HSB) ensures synchronization between active and standby devices. If the HSB channel fails to establish, the following causes are possible:

TCP channel not established: The HSB channel relies on a TCP connection. If the TCP session cannot be established, the backup process cannot start.

Mismatched retransmission settings: If the retransmission count and interval for HSB service packets are inconsistent between the two devices, the synchronization process fails.

Incorrect source and destination configurations: If the source IP address and port number on one device do not match the destination IP address and port number on the other, the channel cannot be established.

Option C is incorrect because the priority of the two ACs affects active/standby roles but does not directly impact HSB channel establishment ​.

 R1 is a Level-1 router in Area 49.0001, while R4 is in Area 49.0004. Level-1 routers only maintain LSDBs for their own area and do not contain LSPs from other areas, such as R4’s LSP.

ï‚· R2 is a Level-1-2 router, so it maintains LSDBs for both Area 49.0001 (Level-1) and Level-2 domains, which include LSPs from R4.

ï‚· R3 and R4, as Level-2 routers, exchange LSPs with each other within the Level-2 domain.

 Thus, the LSDB of R1 does not include R4’s LSP ​.

ï‚· LSP Generation in IS-ISIS-IS routers generate new Link State Packets (LSPs) under the following conditions:

Interface Status Changes: When IS-IS interfaces go up or down, the link state changes, triggering LSP updates.

Periodic Updates: IS-IS periodically regenerates LSPs to ensure link-state information remains synchronized across the network.

Interface Metric Changes: Any modification to interface costs results in a new LSP to reflect the updated cost in the network.

ï‚· Incorrect Option

C. Inter-area IP routes change is incorrect because IS-IS does not inherently differentiate between areas for LSP generation.

ï‚· HCIP-Datacom-Core Reference

IS-IS LSP generation rules are detailed in the IS-IS configuration and implementation chapters​​.

BGP does not advertise all routes learned from peers to other peers. By default, only the best (optimal) routes selected by BGP are advertised to other peers. Additionally, routes learned from IBGP peers are not forwarded to other IBGP peers unless a route reflector or confederation setup is used. The statement claiming all learned routes are advertised is false ​.