CompTIA Exam Prep - ITF+, A+, Network+, Security+, CySA+

Zero touch provisioning lets a device configure itself on first boot. It is unboxed, plugged in, and powered on, and it retrieves its own configuration and firmware without anyone typing a command. For an organization rolling out equipment to hundreds of sites, the alternative — sending an engineer to each one, or shipping pre-staged devices — is the cost this eliminates. The bootstrap chain A factory-default device has no address, no configuration, and no knowledge of where it is. The sequence that fixes that is worth knowing because every step is also a place the process can be attacked. The device brings up its interfaces and requests an address by DHCP . The DHCP response carries not just addressing but vendor-specific options naming a provisioning server and a filename — that is how the device learns where to go next. It fetches a bootstrap script or configuration file from that server, historically over TFTP and increasingly over HTTPS. The script identifie...

This article assumes you know what VXLAN is — the encapsulation, the 24-bit VNI, the VTEP endpoints. If those are unfamiliar, start with VXLAN fundamentals . What follows is the operational layer: how the fabric learns where things are, where the tunnel endpoints should live, and what breaks in practice. Flood-and-learn, and why it was replaced The original VXLAN specification had no control plane. A VTEP learned remote MAC addresses the way a switch always has — by flooding unknown traffic and observing the replies — with multicast in the underlay used to deliver broadcast, unknown unicast, and multicast traffic to every VTEP in the segment. Two problems followed. Multicast in the underlay is operationally unpopular, requiring rendezvous points and a level of multicast expertise many teams do not have. And flooding scales badly: as tenants and endpoints grow, broadcast traffic replicated to every VTEP consumes an increasing share of the fabric. Head-end replicati...

Wireless generations are marketed on peak throughput, and peak throughput is the least useful number for anyone designing a network. What changed in recent generations is how well the medium handles many clients at once , which is the problem real deployments have. The bands 2.4 GHz penetrates walls well and is hopelessly congested, with only three non-overlapping channels and interference from microwaves, cordless devices and Bluetooth. Treat it as legacy support for devices that cannot do better. 5 GHz has many more channels and shorter range, which is an advantage indoors because smaller cells mean less co-channel interference. Parts of the band require dynamic frequency selection, where the access point must vacate a channel if it detects radar — which occasionally causes an unexplained brief outage near airports and weather installations. 6 GHz , available to Wi-Fi 6E and Wi-Fi 7, is the significant addition. A large block of new spectrum, and — the part that mat...

Fibre to the X describes how far fibre runs before copper or coaxial cable takes over for the final stretch. The naming is consistent once you know it, and the differences matter because the copper section determines the speed. The variants FTTP or FTTH — fibre to the premises or home. Fibre all the way to the building, with no copper in the access path. The highest performance and the most expensive to deploy, because every property needs a physical fibre installation. FTTB — fibre to the building. Fibre to a multi-occupancy building, with existing internal copper distributing to individual units. Short copper runs, so performance is close to FTTP. FTTC — fibre to the cabinet. Fibre to a street cabinet, copper from there to the premises, typically a few hundred metres. Far cheaper than FTTP because it reuses the existing copper, and the copper section sets the ceiling. FTTN — fibre to the node, the same idea with a longer copper run and correspondingly...

SD-WAN applies the control-plane and data-plane separation of software-defined networking to wide area connectivity. Branch devices forward traffic; a central controller distributes policy; and the branch chooses which link to send each application over based on that policy and on measured link quality. The same idea as SDN in the data centre, applied to the WAN. The design it replaced Traditional branch networking gave each site an MPLS circuit to headquarters, with all traffic — including internet-bound traffic — backhauled there for inspection before going out. That worked when applications lived in the data centre. Once they moved to cloud services, a branch user reaching a cloud application sent traffic across an expensive private circuit to headquarters and back out to the internet, adding latency for no benefit. MPLS bandwidth is expensive, provisioning takes weeks, and a second circuit for redundancy usually sat idle in an active-standby arrangement. What SD-W...

Power over Ethernet delivers electrical power and data over the same twisted pair cable, so a camera, access point, or phone needs one connection instead of two. The value is not the cable saved — it is that the device can be placed where there is no outlet, and that its power comes from a UPS-backed switch in a wiring closet rather than from whatever socket happens to be nearby. The standards 802.3af , the original, provides 15.4 W at the source and about 12.95 W at the device after cable loss. Enough for a phone, a basic access point, or a fixed camera. 802.3at , called PoE+, raises this to 30 W at the source and roughly 25.5 W delivered. This covers pan-tilt-zoom cameras, higher-capacity access points, and small displays. 802.3bt defines two further types: Type 3 at up to 60 W and Type 4 at up to about 100 W at the source, delivering roughly 51 W and 71 W respectively. These use all four pairs rather than two, and they support laptops, larger displays, and LED lighting. ...