RIP (Routing Information Protocol) is the dynamic routing protocol every textbook teaches first because it is the simplest. Distance-vector, hop count metric, max 15 hops, periodic full updates every 30 seconds. RIPv2 added classless support and authentication. Nobody designs
On a broadcast OSPF segment, the protocol elects a Designated Router (DR) and a Backup DR (BDR). Other routers form adjacencies only with the DR/BDR rather than with every neighbor on the segment, dramatically reducing LSA flooding. The election
OSPF operates differently on different link types. On Ethernet (broadcast), it elects a DR/BDR. On a point-to-point link (PPP, P2P serial, GRE), no election - both ends form an adjacency directly. There are also non-broadcast (NBMA) types
The CCNA exam requires a working understanding of wireless network architecture without a hands-on Wi-Fi lab requirement. The Catalyst 9800 Wireless Controller + lightweight access point design that defines modern Cisco wireless is too large for the CML Free
An SVI (Switched Virtual Interface) is a virtual L3 interface inside a switch, associated with a VLAN. When the switch is enabled for IP routing, the SVI becomes the gateway for hosts in that VLAN - just like a router interface,
A floating static route is a second static route to the same destination with a deliberately higher administrative distance. It sits in the configuration but stays out of the routing table - "floating" - until the primary route disappears. The
A default route - the famous ip route 0.0.0.0 0.0.0.0 next-hop - tells a router "for any destination I do not have a more specific match for, send it here." A floating static
Root Guard is the third spanning-tree hardening feature, after PortFast and BPDU Guard. It protects an interface from EVER becoming a root port. If a switch on the other side of a Root-Guard-enabled port claims to be
Spanning Tree's convergence is fast on RSTP - but it is not instant. When you bring up an access port, STP normally puts it through 15+ seconds of Discarding/Learning before Forwarding, just in case it is connected to
Router-on-a-stick is the classic technique for routing between VLANs using a router with only one physical interface to a switch. The interface becomes a trunk; the router has a virtual subinterface for each VLAN, each with its
CDP (Cisco Discovery Protocol) and LLDP (Link Layer Discovery Protocol) are two ways for network devices to tell each other "hey, I am here, this is who I am, this is what port we are connected on." CDP
An access port normally carries a single VLAN of untagged traffic. There is one important exception: a port connected to a Cisco IP phone (or any device that speaks the same protocol) can carry TWO VLANs simultaneously - one for phone