Border Gateway Protocol (BGP)

Correct Answer: Local Preference

In a network with redundant BGP (Border Gateway Protocol) connections, the 'Local Preference' attribute is used to select a preferred path for specific traffic. It is an indicator to the router which path has priority in its routing decisions. The other options - 'AS Path Length', 'Origin Code', and 'Multi-Exit Discriminator (MED)' - while are also BGP attributes, they don't hold the same level of influence over path selection in this specific scenario. The 'AS Path Length' attribute is used for path vector protocol, in which the number of AS that traffic must pass through to reach a specific network is counted; 'Origin Code' is a code that indicates the origin of the route; and 'Multi-Exit Discriminator (MED)' is used for influencing external neighboring autonomous systems into preferred paths to reach a network within the local AS.

Correct Answer: Route filtering

The process of selectively choosing which routes are allowed in the routing table is known as Route filtering. This term is explicitly used when routes are being denied entry into the routing table, as in the situation described in the question. The option 'Route dampening' is inaccurate because it is a method employed to suppress the instability of flapping routes. 'Conditional advertisement' is a BGP feature used to advertise routes based on certain conditions. Hence, it does not align with the given scenario. Lastly, 'Route aggregation' is the process of combining several routes into one to reduce the size of the routing table, not filtering out routes. Therefore, it does not apply to the problem statement.

Correct Answer: External BGP (eBGP)

The correct session type to establish for exchanging routing information with an Internet Service Provider (ISP) is 'External BGP (eBGP)'. BGP, or Border Gateway Protocol, is a protocol designed to exchange routing and reachability information among autonomous systems on the internet. An External BGP session is established between routers in different autonomous systems, like a company's local network and its ISP, so it's the appropriate choice. On the other hand, 'Internal BGP (iBGP)' is used for exchanging routing information within the same autonomous system. Lastly, 'Open Shortest Path First (OSPF)' and 'Intermediate System to Intermediate System (IS-IS)' are protocols used for routing within an autonomous system, not for communication between different autonomous systems like BGP, so neither could be used to communicate routing information with an ISP.