Used to communicate IP status and error messages between hosts and routers
Uses IP to route its messages between hosts
Must be implemented with IP
remember, IP is just a packet delivery system
transmits and routes datagrams from sources to destinations through a series of interconnected networks
it has a checksum in the IP header to detect lost bits
no error detection on the datagram payload though
but has no native mechanism for source host notification
This is where ICMP comes in
its used to report IP errors to the source host
ICMP data is carried as the payload of an IP datagram
This book is for anyone who wants to master Linux from the command line. When writing it,
I had in mind system administrators, software developers, and enthusiastic users who want to
get things going from the Linux command line. For beginning users, this may be a daunting
task, as Linux commands often have many options documented only in man pages that are not
that easy to understand.
I know it’s kind of wrong to say this type of stuff about your own stuff, but I’m just going to
do it—this is a really good book! It might even be the most interesting book I’ve written so far.
A big reason for this is that its scope allowed me to go above and beyond covering the usual
CCNA study guide material and really detail the commands I used in the guide, plus a lot of
additional commands that just happen to be some of my personal favorites.
Do remember that, although very cool indeed, this volume isn’t intended to be a one-stop
Upon completion of this lab, the student will be able to navigate the DOS command line.
The student will also be able to perform basic file management tasks such as creating
directories and files, navigating through directories, displaying content of directories, and
displaying and changing file attributes.
In addition to the compilers for Visual Basic .NET (vbc.exe), C++ (cl.exe), and C# (csc.exe),
the Microsoft .NET Framework SDK adds a number of tools designed to make it easier
for you to create, deploy, and manage applications and components that target the .NET
Framework. This appendix will introduce these tools and will also detail the command-line
usages of vbc.exe.
CDP discovers and shows information about directly connected Cisco devices, including routers and
switches. CDP is a Cisco proprietary protocol that runs at the data link layer of the OSI model. The
data link layer is Layer 2 of the OSI model. This allows devices that may be running different network
Layer 3 protocols, such as IP or IPX, to learn about each other. CDP begins automatically upon a
device system startup. However, if Cisco IOS Release 10.3 or a newer version is used, CDP must be
enabled on each of the device interfaces. Enable CDP by using the cdp enable command.
This lab helps the student become familiar with the router show commands. The show commands
are the most important information-gathering commands available for the router.
• show running-config (or show run) is probably the single most valuable command to help
determine the current status of a router, because it displays the active configuration file running
• show startup-config (or show start) displays the backup configuration file that is stored
in non-volatile RAM (NVRAM).
Để bắt đầu, bạn cần kích hoạt thanh Command (nếu nó không được kích hoạt sẵn) bằng cách bấm chuột phải vào một vùng trống trên thanh công cụ và chọn Command Bar từ trình đơn ngữ cảnh hiện ra. Bấm vào nút Tools trên thanh Command và chọn Toolbars Disable add- ons từ menu hiện ra. Một hộp thoại có tên là Choose Add-ons sẽ xuất hiện, tại đây, bạn sẽ thấy danh sách các add-on đang có trên IE9 sẽ được liệt kê.
Q: Are pings forwarded by routers?
A: Yes! This is why you can ping devices all over the Internet.
Q: Do all devices forward or respond to pings?
A: No, this is up to the network administrator of the device. Devices,
including routers, can be configured not to reply to pings (ICMP echo
requests). This is why you may not always be able to ping a device.
Also, routers can be configured not to forward pings destined for
This lab you will look at the output of one command the show techsupport
command that combines several common and not so common
commands to provide a snapshot of your device to help technical support
deal with a difficult problem.
In short, spokes of an area peer with the hub through remote-peer command. They have "promiscuous" on so that they can accept peer connections from other spokes. The hub peers with the hub of the next "group" through a remote-peer command, and also has promiscuous on so that it can receive connections from the spokes in its area.
After studying this chapter you will be able to: Be familiar with the ICMP message format, know the types of error reporting messages, know the types of query messages, be able to calculate the ICMP checksum, know how to use the ping and traceroute commands, understand the modules and interactions of an ICMP package.
Thông thường để cấu hình và đặt địa chỉ IP cho các máy trong mạng bạn chỉ cần cấu
hình trong Network Connections và thiết lập địa chỉ IP trong giao thức TCP/IP bằng
giao diện Windows. Nay chúng tôi giới thiệu thêm một phương pháp cấu hình địa chỉ
IP sử dụng câu lệnh Command line đôi khi cách này sẽ được dùng trong các trường
hợp cần thiết
Bước 1. Trong Excel bạn chọn lệnh Tools / Macro / Visual Basic Editor (hoặc ấn tổ hợp phím Alt +
Bước 2. Trong cửa sổ soạn thảo code VBA hiện ra bạn chọn Insert / Module rồi nhập vào phần soạn
thảo bên phải đoạn code
This lab is designed to walk you through a basic VLAN configuration using two Catalyst 1900 (or 2820) series
This lab shows you step-by-step what commands to type in and how to check that you have configured things
correctly. Each switch must be configured with the Enterprise edition software. The Cisco IOS software CLI is not
available if the switch has been configured with the Standard edition software.
Multiprotocol Label Switching
Multiprotocol Label Switching (MPLS) is a standards-approved technology for
speeding up network traffic flow and making it easier to manage. MPLS involves
setting up a specific path for a given sequence of packets, identified by a label put
in each packet, thus saving the time needed for a router to look up the address to
the next node to forward the packet to. MPLS is called multiprotocol because it
works with the Internet Protocol (IP), Asynchronous Transport Mode (ATM), and
frame relay network protocols....
This document contains possible recommended settings for the system
Registry. You can severely impair or disable a Windows NT System with
incorrect changes or accidental deletions when using a Registry editor
(Regedt32.exe or Regedit.exe) to change the system configuration. Currently,
there is no “undo” command for deletions within the Registry. Registry editor
prompts you to confirm the deletions if “Confirm on Delete” is selected from the
options menu. When you delete a key, the message does not include the name
of the key you are deleting.
This guide covers the three remote access to MPLS VPN network architectures: dial, DSL, and cable.
The guide references features described in the Cisco IOS configuration guides and command references.
Consult those documents for additional information. This guide is meant for new and existing MPLS VPN service providers. It includes overview and
configuration information designed to enable users to get their systems running as quickly as possible.
However, it does not include extensive software configuration instructions.
One of the most important aspects of getting a Red Hat Linux system up and running
is configuring the user interface. For most nonadministrative users, this means
configuring the X Window interface. The X Window System is the Linux graphical
user interface (GUI). While the GUI plays an integral part of other operating systems such as
Microsoft Windows, the X Window System on Linux is essentially just another application. Many
administrators don’t even bother with the GUI; the command line interface is enough for most
Ethernet-based data services offer the opportunity to create differentiation, command premium
pricing, and earn higher margins for such value-added data services as transparent LANs, storage
area networks, and virtual private networks. Extending native 10/100Base-T and Gigabit Ethernet
services across the LAN, WAN, and MAN means data services are less expensive to deploy,
provision quickly, and offer exceptional reliability and security.