Speed, Distance, and Cable length are oftened tied together. Copper 100m = 328ft. 50m = 164ft. 37m = 121ft. Category Max Distance and Speed CAT 5 100m - 100Mbps (100BASE-TX) CAT 5e 100m - 1 Gbps (1000BASE-T) 100m - 2.5 Gbps (2.5GBASE-T) 100m - 5 Gbps (5GBASE-T) CAT 6 100m - 1 Gbps (1000BASE-T) 100m - 2....
Layer 1 An Overview For those of you not fimilar Layer 1 refers to the first layer of the OSI model, the physical layer. This layer is technially where 1’s and 0’s cross a medium. But ask any IT professional sometimes just getting the right power or rack screws is hard let alone getting the right cable. I will quick cover some of the basics of the In most cases the medium used for communications is, Fiber Optics, Twised Pair Copper, and Radio Frequecy (Wireless)....
Layer 1 - Copper Copper cables carry low voltage electric signals (NEC defines low volatge systems between 0 and 49 Volts) Back in the day, copper was the medium initally used to cross the counrty back in the days of CW, and Telegrams. With the Advent of the Telephone this copper need to handel more bandwidth and longer distances “twisted pair” copper wires were used for telephone wires. These twised pair wires have evoled over time to bring us to todays CAT6a 10 Gig and Cat8 40 Gig Copper cabling....
Layer 1 - Fiber Optics Fiber Optics uses light (visible and non-visble) to transmit communication signels All Fiber optic cables are made up of sever important compmen Core: is ushally made up of very thin crystal clear glass or platic that allows light to pass through. Think of the core as a guide to help ensure the light passes through to the other side. Cladding: is ushally made up of ### which has a high index of refraction, meaning when light its the cladding at the right angle is it reflected (refracted) back into the core....
Power Power may not techincally be consider part of “Layer 1” but it is a cirtial and often over look part of IT. Below I will go over the basics of power and then go into how it applies to IT. Voltage (V) Electromotive Force or often refered to as electric pressure. Common House voltage (in the US) is 120V but many higher end servers and UPS’s run on 240V....
The OSI Model As many of you likely know the OSI (Open System Interconnection) Model serves as a framework to help struture and organize componets of larger systems into 8 Layers. Understanding the concepts of the OSI model is fundmental to sucess in IT. 7 Layers I will be attmpenting to go through the basics of each layer through different posts. Physical Layer 1 Overview of the Physical Layer Copper Fiber WiFi / RF Power L1 CheatSheet Data Link Layer 2 Network Layer 3 Transport Layer 4 Session Layer 5 Presentation Layer 6 Application Layer 7 Poltics Layer 8 Not a Real Layer
Wireless Security with WPA2 (802.11i) TLDR WEP is insecure WPA1 / WPA using TKIP is also insecure WPA2 is most secure (ensure KRACK is patched) 802.11i is complicated Old Wireless Security WEP / WPA'1' WEP (Wired Equivalent Privacy) Old and Insecure [See Aircrack-NG] (https://www.aircrack-ng.org/) Stream Cipher RC4 CRC-32 Checksum -WPA1 (AKA WPA using TKIP) Has similar attack vectors as WEP **Note 802....
Traceroute is the go-to utility for troubleshooting many network related issues. Overview Traceroute launches a probe packet towards DST IP with a TTL of 1 Every router hop decrements the IP TTL of the packet by 1 When TTL equals 0 the packet is dropped, and the router sends an ICMP TTL exceeded packet to the SRC with the original probe packet as payloads The received message is displayed as a “hop” by traceroute The TTL is incremented by 1 and another probe sent This process is repeated until traceroute receives ICMP Dest Unreachable Probe Packets Each OS has a slightly different of implementing traceroute and its probe packets UNIX uses UDP probes UDP DST port 33434 incrementing once per probe Windows (and some others) use ICMP (each request) probes Look for some traceroute implementation that allows you to use TCP, UDP, or ICMP In most cases, three probes are sent per hop This is why you will see three latency results or *’s These three probes are important as in the case of load balancing path and latency might change Finding problems in your traceroute results Network Latency is normal It takes ~400 ms for a packet to travel across the world (around the equator) just in light propagation Many times ICMP is forwarded, and processed by routers general CPU, which can cause higher than normal delays Note the path your traffic is taking (see below for tips) Tip to understanding traceroute outputs on the internet Look for IATA Airport Code CLLI Codes UN/LOCode Provider names City Names Example Traceroute output from macOS traceroute to google....
The Problem ISE PSNs connect to AD domain controllers to authenticate users on the network. Let’s say there are 4 ISE PSNs and 3 AD Domain Controllers. Seemingly out of no where ISE “backlists” all 3 of our DCs. You only know of this because of the ISE Alarm “joined domain is unavailable” – Hint: Check the AD Connector Report in ISE. The Active Directory Integration Guide for 1.3 will tell you if “AD connector cannot communicate with it [DC] for some reason” it will blacklist that domain controller....