Spanning-Tree Protocol prevents Layer 2 loops by detecting redundant paths and putting one in a blocking state. Rapid-PVST (Rapid Per-VLAN Spanning Tree) is the modern Cisco variant - per-VLAN STP, but using RSTP convergence times (sub-second
EtherChannel can be negotiated by two different protocols: Cisco's proprietary PAgP (Port Aggregation Protocol) or the IEEE standard LACP (Link Aggregation Control Protocol, 802.3ad). LACP is the modern default because it interoperates with everyone. PAgP only works
EtherChannel takes multiple physical links between two switches and bundles them into a single logical link with the combined bandwidth. STP sees the bundle as one link, so no loop. Hashing distributes traffic across the member links. LACP (Link Aggregation
Every CCNA candidate memorizes the OSI seven-layer model and the four-layer TCP/IP model. The exam tests both. What students rarely get is a clear answer to: "okay - which show command lives at which layer?" This
DTP - the Dynamic Trunking Protocol - is Cisco's way of having two switches automatically agree to form a trunk. It works. It is also a security and operational risk: an attacker can plug into a port and convince the
A VLAN is a logical broadcast domain that lives on top of a physical switch. The switch can have a hundred ports but be carved into ten broadcast domains - so a broadcast on VLAN 10 reaches only the ports in
Layer 2 switching boils down to one mechanism: the CAM table (Content-Addressable Memory), also called the MAC address table. The switch builds it dynamically by reading the source MAC of every frame it receives and noting which port that
IPv6 static routes look almost identical to IPv4 static routes. There is one wrinkle worth knowing: when you use a link-local address as the next-hop, you MUST specify the exit interface, because link-local addresses are scoped per-
When the network breaks, the engineer who fixes it first is the one with a method. Trial-and-error works on the third try. A systematic approach to localizing the fault works on the first. This lab teaches you to
GRE - Generic Routing Encapsulation - is the lightest-weight tunnel encapsulation in widespread use. It takes an IP packet, wraps it in another IP packet plus a small GRE header, and ships it across whatever underlay routing happens to exist. No
PPP - Point-to-Point Protocol - is the WAN encapsulation that survived. Frame Relay died, X.25 died, ATM mostly died, but PPP is still on every serial WAN link, every dial-up backup, every long-haul leased line that has
Every IP packet on the planet starts and ends with two 32-bit numbers - the source and destination addresses. CCNA gives you the structure to read those numbers, decide what is local and what is remote, and what your router