Quick Answer

The correct first step is to create a key chain using the key chain command. This is because EIGRP MD5 authentication relies on a key chain to define the actual cryptographic keys and their lifetimes, which the router then uses to generate the MD5 hash for each routing update. Without first establishing the key chain and its associated key string, there is no authentication material to apply. On the ENCOR 350-401 exam, this drag-and-drop sequence tests your understanding of the configuration order: key chain creation, then applying it under the EIGRP router configuration, and finally enabling authentication mode on the interface. A common trap is confusing the order of applying the key chain to the EIGRP process versus enabling it on the interface—remember that the router must first know which key chain to use before the interface can enforce it. A helpful memory tip is “Chain, Claim, Enable”: first build the chain, then claim it under EIGRP, then enable it on the interface.