H12-821 — frequently asked questions

No. An ABR must connect to the backbone area (Area 0) to advertise inter-area routes. Without a connection to Area 0, it cannot participate in inter-area routing.

It cannot exchange routing information with other areas. Routes within that area remain isolated unless a Virtual Link is configured to extend the backbone.

asbr-summary summarizes external routes (Type 5 LSAs) and is configured in the OSPF process view. abr-summary summarizes inter-area routes (Type 3 LSAs) and is configured in the area view.

Yes. If you do not specify 'not-advertise', the router will automatically advertise the summarized route to other areas.

RSTP was designed for rapid convergence. Missing 3 consecutive Hellos provides a quick and reliable signal that the neighbor is down, allowing the port to transition to discarding state immediately without waiting for the longer Max Age timer used in legacy STP.

RSTP consolidates the five legacy STP states into three: Discarding (replaces Blocking and Listening), Learning, and Forwarding. This reduces the time a port spends in non-forwarding states.

FTP uses TCP port 21 for control commands and a separate dynamic port (or port 20 in active mode) for data transfer, keeping control and data streams isolated.

No. Telnet uses a single TCP connection (port 23) to carry both user keystrokes and terminal output simultaneously.

This prefix is assigned by IANA specifically for IPv4 Virtual Router Redundancy Protocol (VRRP) to ensure unique identification across different networks.

No. The VRRP virtual MAC address is generated solely based on the VRID using the formula 00-00-5E-00-01-{VRID}. The IP address is independent.

The default external cost for redistributed routes in OSPF is typically 1.

For Type 1 (E1) routes, add the external metric to the internal cost of the path to the ASBR.

Neither router can become the DR or BDR. They will fail to establish a full adjacency and may get stuck in the Exchange/Loading state.

No. OSPF DR/BDR election is non-preemptive. The current DR keeps its role unless it fails or the interface is reset, regardless of new higher-priority routers joining.

IS-IS has a simpler packet format and uses a hierarchical design that scales better in large core networks. Its separation from the network layer also reduces processing overhead.

Yes, unlike OSPF where areas are defined per interface, IS-IS defines areas per router. An IS-IS router can be configured with up to three area addresses simultaneously.

CLNS is the OSI Layer 3 service IS-IS runs on, not the internal packet format. TLV describes how bits are organized inside the packet to allow flexible expansion.

TLV uses variable-length fields, so new features can be added as new TLVs without changing the base packet type or size, maintaining backward compatibility.

Sub-AS numbers are used to prevent routing loops within the confederation. They allow routers to distinguish between routes learned from different parts of the same physical AS.

No. External peers see the entire confederation as a single Autonomous System defined by the original AS number. The sub-AS details are hidden internally.

The Local zone represents the firewall device itself. Assigning it the highest priority (100) ensures that any traffic destined for the firewall's management interface is strictly controlled and prioritized over traffic passing through other zones.

No, the priority of the default security zones (Local, Trust, Untrust, DMZ) cannot be modified on Huawei firewalls. They are hardcoded into the system to maintain a consistent security baseline.

It generates excessive control plane traffic, increasing CPU usage and potentially causing false session flaps if the device cannot process packets fast enough.

The Wait-to-Restore timer prevents frequent master/backup switchovers when a BFD session is unstable, ensuring traffic remains on the backup until the primary path is stable for a defined period.

No, VRRPv2 is strictly for IPv4. VRRPv3 (RFC 5798) was introduced to support both IPv4 and IPv6.

The default priority is 100. Routers with higher priorities are preferred to become the Master router.

Technically, no. Basic ACLs only match the Source IP address. However, in exam questions, options may group 'Source/Destination IP' to represent IP-layer matching versus MAC-layer matching.

The 'fragment' parameter allows the ACL to identify and match fragmented IP packets, enabling security policies specifically targeting fragmentation attacks.

A time-range activates or deactivates an ACL rule during specified periods, allowing dynamic policy enforcement based on time without modifying the ACL configuration itself.

The default starting ID for Huawei ACL rules is 5. Subsequent rules increment by 5 unless explicitly specified.

No. Route-Policy nodes default to an increment of 10 (starting at 10), while ACL rules default to an increment of 5 (starting at 5).