Huawei H12-821 Exam Questions
HCIP-Datacom-Core Technology V1.0 (Page 3 )

Updated On: 12-Jun-2026

Which of the following attributes must be carried in an Update message?

  1. local-Pref
  2. MED
  3. AS_Path
  4. PrefVal

Answer(s): C

Explanation:

In BGP (Border Gateway Protocol), the AS_Path attribute is one of the mandatory well-known attributes that must be included in every Update message. The AS_Path attribute contains the list of autonomous systems (AS) that the Update message has traversed, which is essential for path selection and loop prevention.



If a router receives two BGP routes carrying the following attributes, which of the following statements is true according to BGP route selection rules?

  1. The optimal route is route N because its MED value is smaller than that of route M.
  2. The optimal route is route N because its AS_Path is longer than that of route M.
  3. The optimal route is route M because its AS_Path is shorter than that of route N.
  4. The optimal route is route M because its MED value is larger than that of route N.

Answer(s): C

Explanation:

BGP uses a series of route selection rules to determine the best route, applied in the following order:
1. Highest Local P


Reference:

Both routes have the same LocPrf (0), so this criterion does not apply here.
2. Shortest AS_Path: Route M has a shorter AS_Path (100) compared to Route N (100 200). This makes Route M the better route at this stage of selection.
3. Lowest Origin Type: Both routes have the same origin (i for IGP), so this criterion does not apply.
4. Lowest MED: This rule is checked only if the AS_Path lengths are equal. Since Route M already wins based on AS_Path, MED is not evaluated in this case.



Which of the following routing policy tools can be used to add or delete an AS path?

  1. filter-policy
  2. community-filter
  3. ip-prefix
  4. ip as-path-filter

Answer(s): D

Explanation:

The ip as-path-filter tool in BGP is specifically used to match and manipulate AS paths. It allows you to perform actions such as adding, modifying, or deleting AS path attributes. This tool uses regular expressions to match specific AS path patterns and apply the desired policies.



BGP routers establish peer relationships using UDP.

  1. TRUE
  2. FALSE

Answer(s): B

Explanation:

BGP (Border Gateway Protocol) establishes peer relationships using TCP, not UDP. Specifically:
BGP uses TCP port 179 for establishing and maintaining peer relationships (sessions).
TCP provides reliable, ordered, and error-checked delivery of messages, which is essential for BGP's operation as it ensures the reliable exchange of routing information.
UDP, being connectionless and less reliable, is not used for BGP peer relationships.



The Hold time in the Open message sent by BGP Peer A is 90s, while that in the Open message sent by Peer B is 30s.
What is the interval for sending Keepalive messages after the two peers establish a connection?

  1. No Keepalive messages will be sent
  2. 90s
  3. 10s
  4. 30s

Answer(s): C

Explanation:

In BGP, the Hold Time is negotiated between peers during the establishment of the session. The lower of the two Hold Times exchanged in the Open messages is chosen as the agreed Hold Time for the session.
Peer A proposes a Hold Time of 90 seconds.
Peer B proposes a Hold Time of 30 seconds.

The agreed Hold Time will be 30 seconds (the smaller value).
The interval for sending Keepalive messages is typically one-third of the negotiated Hold Time:



According to BGP route selection rules, the route with the largest MED value is preferred.

  1. TRUE
  2. FALSE

Answer(s): B

Explanation:

In BGP route selection rules, the route with the smallest MED (Multi-Exit Discriminator) value is preferred, not the largest.
MED is an optional non-transitive attribute used to influence the selection of routes when multiple paths to a destination exist from different autonomous systems (AS).
A smaller MED value indicates a more preferred path.

For example, if two routes have MED values of 50 and 30, the route with the MED value of 30 will be chosen as the preferred route.



Which of the following statements regarding authentication in BGP configuration is true?

  1. A pair of BGP peers must use the same plaintext password.
  2. All BGP peers of a router must use the same password.
  3. All the routers in the same AS must use the same password.
  4. A pair of BGP peers must use the same MD5 password.

Answer(s): D

Explanation:

BGP supports MD5 authentication for securing peer relationships. In MD5 authentication:
Each BGP packet is accompanied by an MD5 hash computed using a shared secret (password) configured on both peers.
For the authentication to succeed, both BGP peers in the session must use the same MD5 password. If the passwords do not match, the BGP session will not be established.



Which of the following statements regarding the output information of a router is true?

  1. This router and its neighbor 2.22.2 are IBGP peers.
  2. The router ID of the router is 1.1.1.1.
  3. The AS number of the router is 100.
  4. This router negotiates with its neighbor using BGP version 3.

Answer(s): C

Explanation:

The output shows Local AS number: 100, meaning the router's Autonomous System (AS) number is 100.
This makes this option correct.



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