H12-821_V1.0 Practice Questions

The asbr-summary command is executed in the global OSPF view to summarize external routes. The abr-summary command is executed in the OSPF area view to summarize routes between areas. By default, the advertise parameter is enabled unless explicitly overridden by the not-advertise option ​.

Hello packets are the most basic and essential type of OSPF packets used for the following purposes:

Neighbor discovery – Routers use Hello packets to discover other OSPF routers on the same link.

Neighbor relationship establishment – When two routers exchange matching Hello packets, they move from the " Init " state to " 2-Way " and further into adjacency states.

Neighbor relationship maintenance – Hello packets are sent periodically to ensure that neighbors are still reachable. If Hello packets are missed within the dead interval, the neighbor is considered down.

Neighbor deletion is not a direct function of Hello packets. Neighbor deletion results indirectly from missed Hello packets.

 IGMP: Manages IPv4 multicast group members and runs on the multicast network ' s last segment (that is, the network segment where a Layer 3 network device is connected to user hosts).

 PIM: Sends multicast data over the network to the multicast device that is connected to group members that have requested the multicast data, implementing multicast data forwarding based on routes.

 IGMP Snooping: Manages and controls the forwarding of multicast data packets to effectively suppress the flooding of multicast data packets on the Layer 2 network.

 IGMP (Internet Group Management Protocol) :

IGMP is used by hosts and adjacent multicast routers to establish and maintain multicast group memberships on a local subnet.

It allows a host to inform a multicast router of its desire to receive multicast traffic for a specific group.

It operates at Layer 3 and runs on the last segment of the network.

Comprehensive and Detailed In-Depth Explanation:

IP Multicast vs. Broadcast:

A.  

TRUE → Unlike broadcast , which sends data to all hosts in a subnet, multicast only sends data to interested receivers , preventing flooding .

B.  

TRUE → Multicast optimizes bandwidth usage by sending a single copy of data , which is then replicated at network routers only when necessary .

IP Multicast vs. Unicast:

C.  

FALSE → Multicast does not improve security ; it may expose data to unintended receivers if not properly controlled .

D.  

FALSE → Multicast reduces the load on the source because a single data stream serves multiple receivers instead of sending individual unicast streams .

???? Reference: Huawei HCIA-Datacom Study Guide, IP Multicast Principles and Benefits.

Comprehensive and Detailed in-depth Step-by-Step Explanation:

BGP (Border Gateway Protocol) uses specific message types to establish and maintain peer relationships between routers. The primary BGP messages involved during the establishment and maintenance of peer relationships are:

Open (D):

The Open message is the first message sent after a TCP connection is established between BGP peers.

It is used to exchange parameters such as the AS number, BGP version, hold time, and BGP identifier.

Keepalive (A):

After the Open message exchange, Keepalive messages are sent periodically to maintain the BGP session.

These messages confirm that the connection is still alive.

Update (C):

Update messages are used to exchange routing information after the peer relationship is established.

They contain information about network prefixes and their associated path attributes.

Hello (B):

Hello messages are not used in BGP. They are typically used in protocols like OSPF or IS-IS to establish and maintain neighbor relationships.

Thus, the correct answers are A (Keepalive) , C (Update) , and D (Open) .