What are three IS-IS PDU types? (Choose three.)
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A. B. C. D. E.BCE
The Intermediate System-to-Intermediate System (IS-IS) is a link-state routing protocol used in computer networks to exchange routing information between network devices. IS-IS defines several Protocol Data Units (PDUs) for exchanging information between devices.
The three types of IS-IS PDUs are as follows:
Database Description (DD) PDU: A DD PDU is used to describe the contents of the sender's Link State Database (LSDB) to a neighboring device. The DD PDU contains a list of LSAs that are present in the sender's LSDB.
Link State (LS) PDU: An LS PDU is used to exchange routing information between devices. It contains information about the sender's network topology, including the list of reachable network nodes and their respective metrics. LS PDUs are periodically sent by each device to advertise their network topology changes.
Partial Sequence Number (PSNP) PDU: A PSNP PDU is used to request missing LSAs from a neighboring device. When a device receives an LS PDU, it checks its LSDB to see if it already has the same LSA. If it does not, it sends a PSNP PDU to request the missing LSA from the sender.
Option A (type length value) is not an IS-IS PDU type, but a general data encoding format used in many networking protocols.
Option C (partial sequence number) is not a valid IS-IS PDU type.
Option E (complete sequence number) is not an IS-IS PDU type.