H12-821 Hcip-Datacom-Core Technology V1.0 Practice Questions

NSSAs are designed to block Type 5 External LSAs but still allow for the redistribution of external routes from within the area. The ASBR within the NSSA generates a special Type 7 LSA to advertise these external routes. Type 7 LSAs are only flooded within the NSSA. When the NSSA's ABR receives a Type 7 LSA, it translates it into a standard Type 5 LSA and floods it into Area 0 and subsequently to other areas. This allows the rest of the OSPF domain to learn about the external routes originated in the NSSA.

A fundamental BGP rule is that when a route is advertised to an iBGP peer, the NEXT_HOP attribute is not changed by default. Therefore, R1 will advertise the route to R2 with the next-hop still set to the IP address of the external eBGP peer. The potential problem is that R2, being an internal router, likely does not have a route in its IGP to reach the external peer's IP address directly. This makes the BGP route unusable. The solution is to configure peer next-hop-self on R1, which forces R1 to substitute its own IP address as the next-hop when advertising to R2.

This is a fundamental difference. OSPF is built around the concept of a mandatory backbone area (Area 0), and all other areas must connect to it. IS-IS uses a two-level hierarchy (Level-1 for intra-area, Level-2 for inter-area/backbone), but the backbone is simply the collection of all Level-2 capable routers, not a specific area. This makes the IS-IS design potentially more flexible. Also, IS-IS runs directly over Layer 2, making it transport-agnostic, whereas OSPF runs over IP.

To match routes based on their BGP community attribute, a community-filter must be created first. This filter defines the community value(s) to match. Then, within the route-policy, the if-match community-filter command is used to reference this filter. This allows the policy to selectively apply actions (like permit or deny) to routes carrying the specified community tag during the redistribution process.

WPA2-Enterprise (or its successor, WPA3-Enterprise) combined with 802.1X is the industry standard for secure corporate wireless. This method meets all requirements: 1) 802.1X forces each user to authenticate with their individual credentials, which are validated by the RADIUS server. 2) It uses strong encryption (AES). 3) It is highly scalable, as user management is centralized on the RADIUS server, making it easy to add, remove, or modify user access without changing the wireless infrastructure configuration. It provides individual accountability, which is impossible with a shared key.

When OSPF routers are in the ExStart/Exchange state, they exchange Database Description (DD) packets to synchronize their Link-State Databases (LSDBs). If the Maximum Transmission Unit (MTU) on their interconnected interfaces is different, the router with the larger MTU might send a DD packet that is too large for the other router to receive. This causes the negotiation to fail and the routers to get stuck in this state, continuously retransmitting DD packets. Mismatched area types or duplicate router IDs would typically prevent the neighbor relationship from forming at all (stuck in 2-Way or earlier).

The Multi-Exit Discriminator (MED) is an optional non-transitive attribute used to influence how a neighboring AS selects an entry point into your AS when multiple entry points exist. A lower MED value is preferred. By setting a lower MED on the routes advertised over the primary link and a higher MED on the backup link, you suggest to the ISP which path to prefer for inbound traffic. Local Preference is used to influence outbound traffic decisions within your own AS. AS_Path prepending is another method, but MED is specifically designed for this purpose.

By default, a Level-1-2 router sets the Attached (ATT) bit in its Level-1 LSP. This signals to other Level-1 routers within the same area that it has a connection to the Level-2 backbone. The Level-1 routers will then install a default route pointing to the L1/L2 router. This mechanism allows Level-1 routers to reach destinations outside their area (including other L1 areas and external routes) without needing to hold all the specific Level-2 routes in their routing tables, thus improving scalability.

This statement is true. A Type 5 External LSA, which advertises an external route, is flooded throughout the OSPF domain. However, the next-hop for this external route is the ASBR. Routers in other areas need to know how to reach the ASBR. The ABR in the ASBR's area generates a Type 4 LSA to advertise the ASBR's router ID and the cost to reach it into other areas, enabling proper routing to external destinations.