H12-821_V1.0 Exam Dumps : HCIP-Datacom-Core Technology V1.0

The MED (Multi-Exit Discriminator) is an optional, non-transitive attribute used to influence the exit path. MED is considered after attributes such as Local-Preference, AS-Path, and Origin during route selection. By default, if a MED value is missing, it is treated as 0 unless the bestroute med-none-as-maximum command is configured to treat it as 4294967295 ​.

Goal Analysis:

Requirement:

The route to 192.168.3.0/24 must exist in R1's and R3's routing tables.

The route must not exist in R2's routing table.

This requires filtering to ensure the route is either:

Blocked on R2's routing table (via filtering on R2), or

Blocked before it is advertised to R2.

Analysis of Each Option:

Option A (Filter-policy on R2 for filtering received routes):

Applying a filter-policy on R2 to filter received routes will block the route from entering R2's routing table but still allow it to propagate to R3.

This meets the requirement.

Option B (Filter-policy on R2 for filtering the routes to be advertised):

Blocking the advertisement of routes from R2 to other routers does not affect the routes received by R2 itself.

This does not meet the requirement but does not affect the propagation to R3.

This is valid if the received route is blocked.

Option C (Filter-policy on R1 for filtering the routes to be imported):

If the route is filtered on R1 during the import phase, the route will not exist in R1’s routing table and thus cannot be advertised to either R2 or R3.

This fails to meet the requirement because the route must exist in R1's and R3's routing tables.

Option D (Filter-policy on R1 for filtering the imported routes to be advertised):

Filtering routes on R1 before advertising to R2 will prevent R2 from receiving the route but allow R1 to advertise the route to R3.

This meets the requirement.

Correct Option:

C (Filter-policy on R1 for filtering the routes to be imported): This will prevent the route from existing in both R1 and R3, violating the stated requirement.

References:

HCIA-Datacom Study Guide, Chapter: OSPF Route Filtering

Huawei OSPF Configuration and Filtering Methods

An OSPF AS-external LSA is used to describe routes to networks that are external to the OSPF Autonomous System (AS). This external route information is typically imported into OSPF by an Autonomous System Boundary Router (ASBR).

If the Forwarding Address field in the AS-external LSA is set to 0.0.0.0, this indicates that traffic destined for the external network should be forwarded directly to the ASBR that advertised the external route.

The specific context mentioned here relates to the Not-So-Stubby Area (NSSA), a type of OSPF area designed to handle AS-external routes in a more controlled way. In NSSAs:

Type 7 LSAs are used to describe AS-external routes.

The ASBR within the NSSA converts the Type 7 LSA to a Type 5 LSA before advertising it to the backbone area.

Hence, the correct acronym for the described functionality is NSSA.

References:

Huawei HCIA-Datacom Study Guide, Chapter on "OSPF Area Types".

RFC 3101 – OSPF Not-So-Stubby Area (NSSA) Option.