In OSPF (Open Shortest Path First), each router maintains aLink-State Database (LSDB), which must be synchronized with other routers in the same area. When an OSPF router receives anLSA (Link-State Advertisement)that it doesnot already have in its LSDB, it takes the following steps:
It updates its LSDB with the new LSA.
It floods the LSA to all its other OSPF neighbors (except the one from which it received the LSA).
This ensures that all routers in the OSPF area eventually converge to the same network topology.
Reference from Huawei HCIP-Datacom-Core Technology Study Guide:
"When an LSA is received and it is newer or not present in the LSDB, the router updates the LSDB and floods the LSA to other neighbors to ensure database synchronization." (Chapter: OSPF Fundamentals - Section: LSDB Synchronization)

All four are valid reasons why IKE (Internet Key Exchange) negotiation might not be triggered:
A- Security policy mismatches canblock data flows, preventing IPsec from initiating.
B- If theroute to the peer is unreachable, no packets can reach the tunnel interface, and IKE will not start.
C- If the IPsec policy is notbound to the correct interface, no protection is triggered.
D- If the ACL doesnot match the actual traffic, the flow will bypass IPsec.
Reference from Huawei HCIP-Datacom-Core Technology Study Guide:
"Common causes of IKE negotiation failure include incorrect ACLs, misapplied policies, unreachable peers, and misconfigured security zones." (Chapter: VPN Technologies - Section: IPsec Troubleshooting)

Edge ports are used in RSTP to bypass the spanning tree calculation for ports connected to end devices. By configuring ports like SWD's GE0/0/2 and SWC's GE0/0/2 as edge ports, they transition directly to the Forwarding state upon activation, ensuring faster convergence. Statement A is incorrect because receiving BPDU invalidates the edge port status .

preference
Explanation:
BGP routes have a variety of path attributes that describe their characteristics and influence route selection.
These attributes include well-known mandatory attributes like AS-PATH and NEXT-HOP, as well as optional attributes like MED and LOCAL_PREF.
In Huawei devices, there is a Huawei-specific attribute called "preference", which is a local parameter used to influence BGP route selection on the device.
* Key Characteristics of "preference":
* It is valid only locally on the router.
* It is not shared with BGP peers.
* It helps the router determine the best route when multiple routes exist for the same prefix.
* It appears in the BGP routing table output in lowercase as preference.
Thus, the correct answer is preference (entered in lowercase as required).
References:
* Huawei HCIA-Datacom Study Guide, Chapter on "BGP Attributes".

Comprehensive and Detailed Step-by-Step Explanation:
* Bidirectional Forwarding Detection (BFD):
* BFD is a lightweight protocol that provides rapid fault detection on links independent of the underlying routing protocol or media.
* Requirements for BFD:
* Both devices at the endpoints of the link must support and configure BFD for it to operate.
* If one device does not support BFD, the feature cannot be used for link detection.
References:
* HCIA-Datacom Study Guide, Chapter: BFD Overview
* Huawei BFD Configuration Guidelines