3IP Connectivity
- 3.1Reading the routing table and the forwarding decision
Covers reading each line of show ip route—the routing protocol code, prefix/network mask, next hop, administrative distance (AD), metric, and gateway of last resort—and the router logic that picks a forwarding path in the order longest match -> AD -> metric, all through diagnosing real device output.
- 3.2Static routing (IPv4/IPv6)
Understands static routing—routes an administrator enters by hand—through its four forms: a network route to a destination network, a host route to a single host, a default route catching all non-matches, and a floating static with a raised AD for backup; and learns to configure and verify ip route / ipv6 route from an operator's viewpoint.
- 3.3Single-area OSPFv2: adjacencies and network types
Covers single-area OSPFv2 (a link-state IGP; AD 110, bandwidth-based cost) through the conditions for forming neighbor adjacencies via Hello (matching area, timers, subnet, MTU), the difference between the point-to-point and broadcast network types, and configuration with router ospf / network / ip ospf verified by show ip ospf neighbor.
- 3.4OSPF DR/BDR election and router ID
Covers the roles of the DR (Designated Router) and BDR (Backup DR) that curb the explosion of adjacencies on a broadcast network, the election decided by priority (default 1; 0 means ineligible) then router ID, the fact that the election is non-preemptive, and how the router ID is chosen in the order manual -> highest loopback IP -> highest physical IP, all through diagnosing the DR/BDR/DROTHER output of show ip ospf neighbor.
- 3.5First-hop redundancy with FHRP (HSRP)
Covers the purpose of FHRP, which makes a host's default gateway redundant, and the operation of Cisco's HSRP—how one Active router forwards for the virtual IP / virtual MAC while a Standby waits, how the role is decided by priority (default 100, higher becomes Active), and the preempt setting needed to fail back after recovery—all from a practical failover-design viewpoint.