2Routing & switching

• 2.1Routing fundamentals

  Covers how a routing table is consulted, when to choose static routing versus dynamic routing, the longest-match rule for resolving multiple matching routes, the default route as the catch-all exit, metric as a route's cost measure, and administrative distance (AD) for comparing routes learned from different sources.

• 2.2Dynamic routing protocols

  Covers the distance-vector approach that evaluates routes by hop count (RIP), the link-state approach that floods link information and computes a shortest-path tree (OSPF, areas, LSAs, cost), the path-vector approach that governs inter-AS routing (BGP, AS, eBGP/iBGP, path attributes), and the distinction between IGP (used within an organization) and EGP (used between organizations), along with the speed of convergence.

• 2.3Switching and VLANs

  Covers VLANs for logically partitioning a single physical switch, tagged VLANs (IEEE 802.1Q) for carrying frames from multiple VLANs over one link, the division of roles between trunk ports and access ports, inter-VLAN routing and Layer 3 switches for communication across VLANs, and link aggregation (LACP) for bundling multiple physical links.

• 2.4STP and loop prevention

  Covers the Layer 2 loop and its harmful consequence, a broadcast storm, that arise when switches are connected redundantly with multiple links; the Spanning Tree Protocol (STP/RSTP) that prevents this; root bridge election, determined by priority and MAC address; and the port states a port transitions through, along with the difference in convergence speed between STP and RSTP.