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Latest posts — page 33

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Lab na-10 - Root Guard

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

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Lab na-09 - PortFast and BPDU Guard

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

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Lab na-12 - Router-on-a-Stick Inter-VLAN Routing

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

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Lab na-11 - CDP vs LLDP

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

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Lab na-05 - Voice VLAN on Access Ports

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

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Lab na-08 - Configure Rapid-PVST

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

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Lab na-07 - PAgP vs LACP

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

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Lab na-06 - LACP Active EtherChannel

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

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Lab nf-12 - OSI vs TCP/IP in the Cisco IOS CLI

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

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Lab na-04 - DTP and Static Trunking

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

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Lab na-02 - VLANs and Access Ports

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