Complete H12-821_V1.0 Huawei Materials

When routes are imported into BGP using the import-route command, the origin attribute is set to incomplete by default. This indicates that the route's origin is not known or is from an external source, as opposed to being explicitly learned through an IGP (IGP) or EGP (EGP) protocol ​.

In OSPF, Database Description (DD) packets are used during the database synchronization process. In the first DD packet a router sends during neighbor establishment, three control bits are set:

I bit (Initial) = 1 → This indicates that the DD packet is the first in the sequence.

M bit (More) = 1 → This means more DD packets will follow.

MS bit (Master/Slave) = 1 → Set by the router assuming the master role in the exchange process.

Setting all three bits to 1 is a standard part of the DD exchange initiation.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“In the initial DD packet, the I, M, and MS bits are set to 1 by the master router initiating database exchange.”

(Chapter: OSPF Operation Mechanism – Section: Neighbor State Machine)

Comprehensive and Detailed In-Depth Explanation:

OSPF uses Hello packets to establish and maintain neighbor relationships. The method of sending Hello packets depends on the network type:

Broadcast networks (e.g., Ethernet) use multicast (224.0.0.5) to discover and maintain OSPF neighbors.

Point-to-Point (P2P) networks (e.g., PPP links) also use multicast (224.0.0.5) for Hello packet exchange.

Non-Broadcast Multi-Access (NBMA) networks (e.g., Frame Relay) require manual neighbor configuration and use unicast Hello packets instead of multicast.

Point-to-Multipoint (P2MP) networks can send Hello packets either unicast or multicast, but it depends on configuration.

???? Reference: Huawei HCIA-Datacom Study Guide, OSPF Neighbor Discovery and Hello Packet Mechanism.

The election of a Designated Router (DR) and Backup Designated Router (BDR) occurs during the OSPF network's initial setup or upon the failure of an existing DR. A new router joining an OSPF network does not automatically preempt the current DR, even if it has the highest priority. DR and BDR elections are not preemptive. The other statements are correct regarding OSPF DR/BDR election processes ​.