Summary

This chapter discusses routing fundamentals, configuration and verification of RIPv2, EIGRP, and OSPFv2 unicast routing protocols on NX-OS, multicast fundamentals, and PIMv2 configuration and verification on NX-OS, including the following points:

• Layer 3 unicast routing involves two basic activities: determining optimal routing paths and packet switching.
• Routing algorithms use many different metrics to determine the best path to the destination.
• An autonomous system (AS) is a portion of an internetwork under common administrative authority that is regulated by a particular set of administrative guidelines.
• An administrative distance is a rating of the trustworthiness of a routing information source. A higher value indicates a lower trust rating.
• Routing protocols that route packets between autonomous systems are called exterior gateway protocols or interdomain protocols. Routing protocols used within an autonomous system are called interior gateway protocols or intradomain protocols.
• Distance vector protocols use distance vector algorithms (also known as Bellman-Ford algorithms) that call for each router to send all or some portion of its routing table to its neighbors.

In link-state protocols, also known as shortest path first (SPF), each router builds a link-state advertisement (LSA) that contains information about each link and directly connected neighbor router and shares the information with its neighboring routers.

The Routing Information Protocol (RIP) is a distance vector protocol that uses a hop count as its metric.

The Enhanced Interior Gateway Routing Protocol (EIGRP) is a unicast routing protocol that has the characteristics of both distance vector and link-state routing protocols. By default, EIGRP uses the bandwidth and delay as its metrics.

• OSPFv2 is a link-state protocol that uses a link cost as its metric and uses link-state advertisements (LSAs) to build its routing table.
• Multicast involves both a method of delivery and discovery of senders and receivers of multicast data, which is transmitted on IP multicast addresses called groups.
• A multicast distribution tree represents the path that multicast data takes between the routers that connect sources and receivers. Protocol-Independent Multicast (PIM) is used to dynamically create a multicast distribution tree.
• IGMP is used to dynamically register individual hosts in a multicast group on a particular LAN. IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their content.
• MSDP enables RPs to share information about active sources across PIM-SM domains.