Which three OSPF parameters must match before two devices can establish an OSPF adjacency? (Choose three.)
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A. B. C. D. E. F.BEF.
When OSPF routers are connected to the same network, they can establish an adjacency to exchange routing information. Before the adjacency can be formed, the routers must agree on certain parameters. The following OSPF parameters must match between the two routers:
A. IP address: OSPF routers must have the same IP address on the same network segment. This is typically configured on the interface level.
B. Subnet mask: OSPF routers must have the same subnet mask for the IP address configured on the interface. If the subnet masks do not match, the routers will not be able to form an adjacency.
E. Area number: OSPF routers must be in the same area to form an adjacency. If the routers are in different areas, they will not be able to form an adjacency.
In summary, the three OSPF parameters that must match before two devices can establish an OSPF adjacency are IP address, subnet mask, and area number. Other OSPF parameters that must be the same include authentication type, authentication key, and OSPF interface type. However, these parameters are not included in the answer choices provided. The OSPF process ID and hello timer setting can be different on each router and do not need to match for the adjacency to form.