Which two IS-IS parameters must match before two Level 2 peers can form an adjacency? (Choose two.)
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A. B. C. D. E.BE.
https://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/200293-IS-IS-Adjacency-and-Area-IS-IS (Intermediate System to Intermediate System) is a link-state interior gateway protocol used in service provider networks to exchange routing information between network devices. To establish a Level 2 IS-IS adjacency, two devices must meet specific requirements. Two of these requirements are:
A. Hello Timer Setting: Before two IS-IS Level 2 peers can establish an adjacency, the Hello timer value on both sides must be the same. Hello messages are sent at regular intervals to keep the neighbor relationships active. If a device receives a Hello message from a neighbor, it assumes that the neighbor is still active. If a device does not receive a Hello message from a neighbor within the Hello timer period, it assumes that the neighbor is no longer active, and the adjacency is lost.
B. System ID: IS-IS uses a System ID to identify each router in the network. The System ID is a unique 6-byte number that identifies each device in the network. Before two Level 2 IS-IS peers can establish an adjacency, their System IDs must match. The System ID is usually derived from the device's MAC address or configured manually.
Therefore, the correct answer is A. hello timer setting and D. system ID. Authentication settings, area ID, and MTU are not mandatory parameters to form an adjacency, although they can be configured optionally for security, scalability, and performance reasons.