Which of the following Hello packets are used in IS-IS?

The Level-1 LAN IIH (Intermediate Hello) packet is a fundamental part of the IS-IS (Intermediate System to Intermediate System) routing protocol, which is used in dynamic routing environments. This packet is utilized by Level-1 routers to communicate with other Level-1 routers within a specified area. The primary purpose of the IIH packet is to establish and maintain neighbor relationships, allowing routers to share relevant routing information and topology data.

In an IS-IS network topology, routers can function at multiple levels (Level-1 and Level-2) to support both intra-area and inter-area communication. The Level-1 LAN IIH specifically indicates the level at which the packet is being transmitted, which is crucial for proper routing decisions within the network's hierarchy. Additionally, this packet can contain information about the router's capabilities and state, which enhances the efficiency of the routing process.

Understanding the role of this packet is vital for networking professionals working with IS-IS, as it lays the groundwork for neighbor discovery and the establishment of a reliable link-state database. This foundational knowledge is essential for effective network design and troubleshooting within IS-IS environments.