if you walk the footsteps of a stranger you'll learn things you never knew, you never knew: October 2018

10/31/18

10/29/18

10/28/18

Check port cmd with multi-thread C#.

Source C#
https://pastebin.com/egbykfAh

10/21/18

CCNA (Cisco Certified Network Associate) is a certification from Cisco, the world’s most famous company that manufactures and sells networking equipment. This certification helps you to become familiar with a wide range of topics, including:

LAN/WAN
OSI and TCP/IP model
VLANs
Ethernet
Switches and routers
Network utilities (ping, tracert, arp)
IP addressing
Subnetting
Routing protocols (RIP, EIGRP, OSPF)
WLAN
NAT
ACLs

This website will try to cover all of these topics.

How to become CCNA certified?

You can become CCNA certified in two ways:
1. by passing the CCNA 200-125 CCNA exam ($325).
2. by passing the ICND1 100-105 exam and ICND2 200-105 (165 $ each).
The CCNA 200-125 exam covers the topics from both ICND exams.

NOTE
If you pass the ICND1 exam, you will receive a certification called CCENT (Cisco Certified Entry Networking Technician).

The CCNA 200-125 exam consists of 60-70 questions. The ICND exams have 45-55 questions. The highest score you can achieve on either exam is 1000. The minimum passing score is somewhere around 830.

Where to take the exam?

To take the CCNA exam you have to schedule a test appointment through Pearson VUE, an electronic testing company. Pearson VUE has many authorized testing centers throughout the world and you can locate a test center in your vicinity.
The exams are available in English and Japanese and lasts for 90 minutes, unless you aren’t a native speaker of any of these two languages. If that is the case, you will get a 30 minutes time extension. After finishing the test you will immediately get the results. Cisco provides just the basic information about your score, so you can’t be sure which questions you got right or wrong!

Preparing for the exam

There are several ways in which you can prepare yourself for the exam:

attending a CCENT or CCNA course – Cisco courses are offered by various educational companies and institutions. You can use this online tool to locate an academy in your vicinity. These courses usually lasts a couple of months and include a lot of hands-on activities. Prices vary depending on your location, but the courses can be quite costly (up to $1000).
self-study with textbooks and online courses – another popular way to prepare a CCENT exam is by self-studying. There are lots of high-quality resources online and tools such as GNS3 or Packet Tracer that enable you to study without actually buying expensive equipment. Of couse, this website is one of these high-quality online resources :-). Many people use website like Ebay or Amazon to find CCNA kits that will enable them to work on real equipment.
concentrated boot camps – intensive, week-long live classes that cover months of materials in just five days. Not recommened for beginners.

NOTE
You don’t need to attend a course academy in order to take the CCENT or CCNA exam.

Exam content

On the ICND1 exam, you can expect to be questioned about topics such as the operation of IP data networks, LAN switching technologies, IPv6, IP routing protocols, IP services such as DNS, DHCP, TFTP, and NTP, basic troubleshooting… On the ICND2 exam, expect questions regarding configuration and troubleshooting of STP, routing protocols, QoS concepts… The CCNA exam includes the questions from both ICND exams.
Cisco has published the general guidelines for the content likely to be included on the exam:

Cấu trúc Router Cisco

The following list details the four main types of memory found in Cisco switches, routers, as well as the most common use of each type:

RAM: Sometimes called DRAM, for dynamic random-access memory, RAM is used by the
switch, router just as it is used by any other computer: for working storage. The running (active)
configuration file is stored here.

ROM: Read-only memory (ROM) stores a bootstrap (or boothelper) program that is loaded
when the switch first powers on. This bootstrap program then finds the full Cisco IOS image
and manages the process of loading Cisco IOS into RAM, at which point Cisco IOS takes over
operation of the switch.

Flash memory: Either a chip inside the switch or a removable memory card, flash memory
stores fully functional Cisco IOS images and is the default location where the switch gets its
Cisco IOS at boot time. Flash memory also can be used to store any other files, including
backup copies of configuration files.

NVRAM: Nonvolatile RAM (NVRAM) stores the initial or startup configuration file that is
used when the switch is first powered on and when the switch is reloaded.

---------------224

Cấu trúc 1 router cisco gồm nhiều thành phần,

-NVRAM(Nonvolatile Random access memory) là 1 loại Ram đặc biệt có thể lưu trữ thông tin dữ liệu kể cả khi mất điện.
+chứa file startup config
+chứa thanh ghi cấu hình phần mềm (Configuration register is 0x2102) dùng để xác định os image trong quá trình boot.

-FLASH: bộ nhớ lưu toàn bộ hệ điều hành Cisco IOS

-ROM: Read Only Memory: là nơi lưu trữ đoạn mã của chương trình kiểm tra khi khởi động. Nhiệm vụ chính của ROM là kiểm tra phần cứng khi khởi động, sau đó chép phần mềm Ciso IOS từ flash vào RAM. Nội dung trong bộ nhớ ROM thì không thể xóa được.

Phần 2:

Các interface trên router.

Interface trên switch

Cáp console cấu hình thiết bị Cisco

Các giá trị tốc độ truyền dữ liệu chuẩn của COM: 50,75,110,750,300,600,1200,2400,4800,9600,19200,28800,38400....56600,115200 bps

if you walk the footsteps of a stranger you'll learn things you never knew, you never knew

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