OSPF Authentication MD5 Key

MD5 authentication uses an encoded MD5 checksum that is included in the transmitted packet. The receiving routing device uses an authentication key (password) to verify the packet. If MD5 is enabled on an interface, that interface accepts routing updates only if MD5 authentication succeeds. Otherwise, updates are rejected. The routing device only accepts OSPFv2 packets sent using the same key identifier (ID) that is defined for that interface.