On the OSPFv3 network shown in the figure, OSPFv3 is enabled on the interfaces connecting R1, R2, and R3. The router ID of each router is 10.0.X.X, where X is the number of the router. If you check detailed information about an LSA on R3, the command output shows that the LSA is generated by R2 and describes the IPv6 prefix address associated with the Router-LSA.
On the network shown in the figure, IS-IS runs on R1, R2, R4, and R5, and the area ID is 49.0001. IS-IS runs on R3 and R6, and the area ID is 49.0002. The import-route isis level-2 into level-1 command is configured on R2 and R5. In AS 65000, R1, R3, R4, and R6 each establish iBGP peer relationships with R2 and R5. R2 and R5 are RR (Route Reflectors), and R1, R4, R3, and R6 are the iBGP peer relationship clients. The iBGP peer relationship ID is 10.0.0.X/32, where X is the number of the iBGP router. R1 and R4 import the external route 192.168.1.0/24 to BGP through the import-route command, and R3 and R6 import the external route 192.168.2.0/24 to BGP through the import-route command. Which of the following statements are true?
Comprehensive and Detailed In-Depth
This question involves a complex network topology with IS-IS, iBGP, and route reflection, requiring an understanding of routing protocols, area boundaries, and route distribution. Let's analyze each statement step-by-step to determine which is true, based on HCIP-Datacom principles.
Network Overview:
IS-IS Configuration:
IS-IS runs on R1, R2, R4, and R5 in area 49.0001 (Level-1/Level-2).
IS-IS runs on R3 and R6 in area 49.0002 (Level-2 only, as implied by the figure).
The import-route isis level-2 into level-1 command on R2 and R5 allows Level-2 routes (from area 49.0002) to be injected into Level-1 routers (R1, R4) in area 49.0001.
BGP Configuration:
AS 65000 uses iBGP with R2 and R5 as Route Reflectors (RRs), and R1, R3, R4, and R6 as clients.
iBGP peer relationships use IP addresses 10.0.0.X/32, where X is the router number (e.g., R1 = 10.0.0.1/32, R4 = 10.0.0.4/32, etc.).
R1 and R4 import the external route 192.168.1.0/24 into BGP using import-route.
R3 and R6 import the external route 192.168.2.0/24 into BGP using import-route.
Topology Insights:
The figure shows R2 and R5 as central hubs connecting Level-1/Level-2 IS-IS areas and serving as RRs for iBGP.
R1 and R4 are in area 49.0001 (Level-1/Level-2), while R3 and R6 are in area 49.0002 (Level-2).
External routes (192.168.1.0/24 and 192.168.2.0/24) are injected into BGP and distributed via iBGP.
Analyzing Each Statement:
A . The routing table of R4 contains two equal-cost default routes.
Analysis:
In IS-IS, default routes (0.0.0.0/0) are typically generated by Level-2 routers and propagated to Level-1 routers if configured (e.g., via default-route-advertise).
R4 is a Level-1/Level-2 router in area 49.0001. It can learn default routes from R2 or R5 (Level-2 routers) if they advertise a default route.
However, the question does not indicate that R2 or R5 are configured to advertise default routes, nor does it specify equal-cost paths to a default route.
Given the import-route isis level-2 into level-1 on R2 and R5, Level-2 routes (including defaults, if any) are injected into Level-1, but there's no evidence of two equal-cost default routes in R4's routing table.
Additionally, IS-IS prefers the closest Level-2 router for default routes, and the topology suggests a single path (e.g., via R2 or R5), not two equal-cost paths.
Conclusion: This statement is false.
B . The route 192.168.2.0/24 in the routing table of R4 has two different outbound interfaces.
Analysis:
The route 192.168.2.0/24 is an external route imported into BGP by R3 and R6 (in area 49.0002) using import-route.
As RRs, R2 and R5 reflect this route to their iBGP clients, including R4 (in area 49.0001).
However, iBGP routes do not modify the next-hop by default unless next-hop-self is configured on the RR. The next-hop for 192.168.2.0/24 from R3/R6 would typically point to R3 or R6, not R2 or R5, unless modified.
R4, as an iBGP client, receives the route but needs an IGP (IS-IS) path to the next-hop (R3 or R6).
The import-route isis level-2 into level-1 on R2 and R5 allows R4 to learn IS-IS routes from area 49.0002, but the question does not indicate multiple equal-cost paths to R3 or R6 from R4.
In IS-IS, unless explicitly configured for equal-cost multipath (ECMP) with the same cost to R3 and R6, R4 would use a single outbound interface to reach 192.168.2.0/24.
The topology suggests a single path (e.g., via R2 or R5) to area 49.0002, not two equal-cost outbound interfaces.
Conclusion: This statement is false.
C . The routing table of R1 contains two equal-cost default routes.
Analysis:
Similar to R4, R1 is a Level-1/Level-2 router in area 49.0001. It can learn default routes from R2 or R5 if they advertise them.
The question does not specify that R2 or R5 are configured to advertise default routes, nor does it indicate multiple equal-cost paths to a default route.
IS-IS prefers the closest Level-2 router for default routes, and the topology (with R2 and R5 as central hubs) suggests a single path, not two equal-cost paths.
Without evidence of ECMP or specific default route configuration, R1 would not have two equal-cost default routes.
Conclusion: This statement is false.
D . The routing table of R1 contains the route 192.168.2.0/24.
Analysis:
The route 192.168.2.0/24 is an external route imported into BGP by R3 and R6 (in area 49.0002) using import-route.
R2 and R5, as Route Reflectors, reflect this iBGP route to their clients, including R1 (in area 49.0001).
iBGP ensures that the route is propagated within AS 65000, so R1, as an iBGP client of R2 and R5, will receive the 192.168.2.0/24 route.
For R1 to install this route in its routing table, it needs a valid IGP (IS-IS) path to the next-hop of the BGP route (likely R3 or R6).
The import-route isis level-2 into level-1 on R2 and R5 ensures that IS-IS Level-2 routes from area 49.0002 (including paths to R3 and R6) are injected into Level-1 routers like R1.
Therefore, R1 can resolve the next-hop for 192.168.2.0/24 via IS-IS and install the route in its routing table.
Conclusion: This statement is true.
Final Answer and Rationale:
The only true statement is D, as R1, being an iBGP client of R2 and R5, will receive and install the 192.168.2.0/24 route in its routing table, with IS-IS providing the necessary path to the next-hop.
Reference from HCIP-Datacom-Advanced Routing & Switching Technology Documents:
Huawei HCIP-Datacom V1.0 Training Manual, Chapter 4: IS-IS Configuration and Optimization, Sections on Level-1/Level-2 Interactions and Route Import.
Huawei HCIP-Datacom V1.0 Training Manual, Chapter 5: BGP Configuration and Optimization, Sections on Route Reflection and iBGP Route Distribution.
RFC 1195 (IS-IS) and RFC 4271 (BGP-4) for standard protocol behavior.
The figure shows information about an LSP (Link-State PDU) generated by an IS-IS router.
From the LSP, you can infer that the router is not the DIS (Designated Intermediate System) of the local link.
Options:
Comprehensive and Detailed In-Depth
1. Understanding the DIS (Designated Intermediate System) in IS-IS
In IS-IS, the DIS (Designated Intermediate System) is similar to the DR (Designated Router) in OSPF.
Unlike OSPF, IS-IS does not use an election based on priority; instead, the router with the highest priority becomes the DIS.
If there is a tie in priority, the router with the highest MAC address on the interface becomes the DIS.
The DIS is responsible for generating additional LSPs (pseudonode LSPs) for the link and synchronizing the database between routers.
2. How to Identify If the Router Is the DIS from the LSP
In the given LSP output, there are NO pseudonode LSPs (LSPs ending with .01).
The DIS is responsible for creating pseudonode LSPs, which represent a multi-access network in the IS-IS topology.
If the router were the DIS, it would generate both its own LSP (ending in .00) and a pseudonode LSP (ending in .01).
Since we only see an LSP ending in .00, this confirms that the router is NOT the DIS.
3. Evaluating the Answer Choices
Option A (TRUE) -- Correct:
Since no pseudonode LSP is present, the router is not the DIS.
This confirms that the statement is TRUE.
Option B (FALSE) -- Incorrect:
If the router were the DIS, it would generate pseudonode LSPs, but they are missing from the output.
Therefore, the statement is NOT false.
Final Answer:
Answe r: A (TRUE)
HCIP-Datacom-Advanced Routing & Switching Technology Reference:
IS-IS Designated Intermediate System (DIS) Selection Process
Pseudonode LSP Generation in Multi-Access Networks
IS-IS LSP Structure and Identification of DIS
On the network shown in the figure, VRRP is configured on Rl and R2, and the virtual IP address is 10.0.12.254. After the configuration is complete, the network engineer checks the VRRP status on R1 and R2, and finds that both devices are in the Master state. Which of the following is not a possible cause of this problem?
BFD for OSPF refers to the association of BFD with OSPF to speed up OSPF's response to network topology changes. The OSPF neighbor relationship can enter the Full state only after the BFD session goes up. The OSPF neighbor relationship can go down only after the BFD session goes down.
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