ABSTRACT
This chapter presents several experiments that illustrate the designated router election process in Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS). It addresses the Hello protocol and explores the designated router election and explains the flooding and deletion procedures. The chapter illustrates the initial Link State Database synchronization process. It examines the process for the case of OSPFv2 shared links and also explores the various types of adjacencies in IS-IS, as determined by the interface type L1-only, L2-only, and L1/L2, and the declared addresses. The source and destination indicated by Wireshark are the MAC addresses, since IS-IS control packets are directly encapsulated in layer-2 packets. The verification of bidirectional relationships is done differently in IS-IS point-to-point links. The chapter addresses three different cases: cold start, change of Designated Intermediate System (DIS), and DIS failure.
