Harris Andrea asked:


Since Cisco Certifications are always hot and the Cisco CCNA is the most popular from all, I decided to start a series of articles regarding important topics that you need to be prepared for passing the CCNA 640-802 composite exam. These topics will be also useful for people taking the two-exam option (ICND1 640-822 and ICND2 640-816).

The CCNA exam will test your ability to understand the Internet Layer of the TCP/IP model, and specifically you must be able to describe the components and structure of an IPv4 address, compare public and private addresses, differentiate between the classes of IP addresses, define the function of DHCP and DNS in IP addressing etc. So let’s see some important concepts below:

– Each internet network host (computer, router, server etc) has its own unique IP address to communicate with other hosts. It is like the unique postal address of our home. There are two versions of IP addresses available. IPv4 and IPv6. The IP version 4 type is the most common today but in the future the IP version 6 will dominate. IPv4 is a 32-bit address and IPv6 is 128-bit address.

– IP addresses can be assigned to hosts either manually or dynamically. Dynamic assignment uses the Dynamic Host Configuration Protocol (DHCP).

– The purpose of DNS is so resolve domain names to IP addresses.

– An IPv4 address (32 bits) is broken into 4 sections with 8 bits each. Although the IP address is a binary number, we represent it into decimal notation.

– An IP address (IPv4) consists of the Network ID (leftmost or high-order bits) and the Host ID (rightmost or low-order bits). The subnet mask specifies what is the Network ID and what is the Host ID. For example an IP address 192.168.10.20 with subnet mask 255.255.255.0 specifies that the Network ID is 192.168.10 and the Host ID is 20. Also, an IP address 10.1.2.30 with subnet mask 255.255.0.0 specifies that the Network ID is 10.1 and the Host ID is 2.30. You get the point now.

– We have public and private IP addresses. Public addresses are always unique but private addresses can be reused in private LAN networks. The Private addresses are within the following ranges:

10.0.0.0 through 10.255.255.255 172.16.0.0 through 172.31.255.255 192.168.0.0 through 192.168.255.255

– As the number of networks grew, the IP addresses were broken into categories called classes to accommodate different sizes of networks. We have five classes of IP addresses. Class A, B, C, D, E.

– Any address that starts with a value between 1 and 126 in the first decimal octet is a Class A address. E.g 10.1.2.24 is a Class A address.

– Any address that starts with a value in the range of 128 to 191 in the first octet is a Class B address. E.g 172.16.1.27 is a Class B address.

– Any address that starts with a value in the range of 192 to 223 in the first octet, it is a Class C address. E.g 192.168.5.1 is a Class C address.

– An IP address that starts with a value in the range of 224 to 239 in the first octet is a Class D address. Class D address range is used for multicasting. E.g 224.0.0.1

– Any address that starts with a value between 240 to 255 is a Class E address. These addresses are reserved and not used anywhere.



Carol

Elizabeth Catalanotto asked:


Imagine spending countless hours optimizing your website only to discover that it’s still not ranking any higher. What could possibly be holding your site back? After all your code is search engine friendly, the content has been rewritten to ensure its topic relevancy, and you’ve managed to score some pretty good links to your site.

If everything seems to be in place, you may be surprised to find out that you’ve overlooked a crucial step in the SEO process.

Just when you think you’re site is performing at its best you learn the awful truth - your web server is hindering your search engine ranking.

Selecting a server is often overlooked as a step in the SEO process. However, it is a crucial first step that each SEO professional should address when beginning any project. There are seven key areas that search engines now consider when ranking websites that could be affected by your web server.

Uptime Your web server’s guaranteed uptime is a major factor that can affect your site’s ranking. The uptime of your site is so important because if it isn’t up and running then there is no way for the search engine spiders to crawl your pages. To ensure that your site is at its best availability don’t settle for a web server that offers anything less than 99.9% uptime.

Name Servers Do you know who else is on your name server? Well, even if you don’t know all of the major search engines do. They can identify all of the domain names with which you share a name server. This can be bad news for you ranking if you happen to share your name server with a large number of spam sites.

IP Classes Search engines group websites into neighborhoods based on their IP addresses. A search engine can detect what types of websites are hosted on a Class C IP address, and you could be penalized if your site is mixed into a bad neighborhood.

Sharing an IP Address Chances are that you are just one of the many clients that your web server has assigned to a single IP address. This could mean that you are in some bad company if one of those sites breaks the rules of one or more search engines then you run the risk of being banned with them. You see it is much easier for a spammer to obtain a new domain name than a new IP address so many search engines choose to ban the IP address instead of the domain name.

Response Time Search engine spiders are busy programs and therefore have very limited time to crawl through each site. If your website has a slow response time then it will take longer to read each page and the spiders will have to move on before crawling all of your pages.

Date Modified Attribute Another aspect of your web server to keep in mind is whether it supports the Date Modified attribute or not. Major search engines like Google are constantly checking the dates that documents are created to determine the average age of the documents on your site and how frequently pages are updated or changed. If your web server doesn’t support the Date Modified attribute then the search engines are unable to collect this pertinent information from your site.

301 Redirect Capabilities Search engines see the www domain and the non-www domain as separate sites, but 301 redirects help to avoid the possibility of duplicate content penalties. Ideally, your server should automatically issue a 301 server site redirect to any request made for a non-www domain that forwards users to the www domain.

Check out your web hosting server to determine if your host is keeping your ranking down. Ask them about these important factors to see where their service stands. Were they selective when you signed up for hosting or were they willing to give up the space without asking any questions?

On the other hand, if you are a web host keeping these criteria in mind can help you to provide a better quality service to your customers. Services that determine whether or not your servers are SE friendly are available from SEO Certified Servers.



Gordon

webpromotionz asked:

HANDYMAN-diy tips and safety info. from myhomehandyman.co.uk Here we are looking at electrical bonding in the house and the safety aspects of electrical bonding. Relaible affordable handyman service covering London,herts,kent and surrey created by webpromotionz.co.uk web promotionz web design seo hosting video production internet marketing … builder carpenter electrician Handyman painter plumber

Susan

Alicia Hilton asked:


Organizations can realize huge savings by migrating SNA applications to IP using TN3270 and TN5250, eliminating the need for older, cost intensive SNA communication hardware and software.

IBM’s Systems Network Architecture (SNA) is a protocol stack that IBM developed to address networking deficiencies that were prevalent at the time of its creation in 1974. Several large hardware and software vendors provide SNA gateways that connect LAN-based PCs with IBM host systems running SNA (Systems Network Architecture) protocols, including IBM, Microsoft and Hewlett Packard.

In the 1990’s, fueled by a Gartner Group report stating that “users with SNA as their primary protocol will spend a total of 20% more than IP users on training staff, hardware and software purchases, and administration”, organizations began to migrate to Internet Protocol based networks.

Now available on the market are non-invasive integration server solutions that allow customers to replace costly, aging SNA solutions with programmatic access to host-based applications at the data stream layer over an IP network. The host applications will traditionally be using 3270 (IBM Mainframe or zSeries) or 5250 (IBM AS/400 or iSeries) protocols and using LU types 0, 1, 2 or 3. A class library can be used to simply expose the information contained in these protocols to the customer’s application prior to the construction of the screen and print buffers. This should not be compared to “screen scraping” API’s such as HLLAPI or Object API offered by most terminal emulation vendors.

Typical customer applications requiring this interface are found in the banking and financial worlds, especially where the migration from SNA to IP networks has not yet been fully achieved. With the current state of the economy, some of the largest banks in the United States are now using this technology to eliminate thousands of servers and realize considerable savings in the process.

Many organizations continue to use host printing, whether from an IBM zSeries mainframe, iSeries AS/400 midrange or UNIX server. Using this type of programmatic IP-based integration solution, a developer could take a standard IBM 3287 LU 1 or 3 mainframe host printer session and programmatically output the information to multiple formats, including PDF, HTML, fax or file. This requirement can be found in banks, hotels, car rental agencies, hospitals, universities and state and local governments that continue to use host applications and need to output statements, receipts, invoices, reservations, class schedules, tax information, etc. in multiple output formats.

Using the LUA-RUI interface, existing LUA-RUI applications can be migrated from older, expensive SNA hardware and software solutions. Using the LUA RUI interface permits more control in customer applications by providing methods to handle exception requests, minimize LAN traffic through program design and recover from session failures.



Katie

Vikram kuamr asked:


An Internet Protocol (IP) address is a logical address assigned to devices participating in a network that utilizes the IP for communication between nodes. Although normally stored as binary numbers, an IP address is usually displayed in forms or notations that are readable by humans.

Every time someone requests a webpage or sends emails, a part of the information includes the IP address. At the other end, the recipient can see the IP address of the one that sent an email or requested an HTML webpage.

In short, the role of an IP address is characterized as a name that indicates what we are looking for, an address where one can be able to locate it, and the route that one needs to get there, without any further hassle.

The original designers of the IP address came up with a 32-bit Internet Protocol version 4 (IPv4), which is still widely used today. But due to the huge growth of the Internet, they have developed a new addressing system, the 128-bit Internet Protocol version 6 (IPv6).

An IP address specifies the locations of the sources and destination nodes of the routing system. This is why some of the bits in an IP address are used to comprise a subnetwork. An IP address may be private for use on a Local Area Network (LAN), or for the use on the Internet thus making it public.

The Design

The IP address was earlier intended to be uniquely designed for a single computer or device but this isn’t always necessary, since some private networks create their own addresses. Besides, some technologies redesigned their system to be able to allow multiple hosts for a single address but its place depends on the request of the clients in the network.

More Info

In an isolated network, one can assign an IP address at random as long as each one is unique but if one is about to connect to a private network, a registered IP address is needed so as not to be hassled with duplicates.

In the early stages of Internet protocol, the administrators interpreted IP address as a structure of host and network number.

The Parts

The IP address has two parts, which is the identifier of the particular network and the device within that network. On the Internet though, especially when administrators ping IP, only the network part is important because it is the only one that is looked at.

The Classes and Their Formats

Networks vary in size and that is why there are four formats of IP addresses:

?        CLASS A addresses are for large networks with many devices

?        CLASS B addresses are for medium sized networks

?        CLASS C are for smaller networks which have fewer than 256 devices

?        CLASS D are multicast address

The address class format is indicated by the first few bits of the IP address itself.

Usually, the IP address is written as four decimal numbers each of them representing 8 bits and is separated by periods. This form is more technically known as the dotted quad notation.

To put it bluntly, an IP address is a 32-bit number that identifies either the sender or receiver of certain information. When you use the command ping IP, this is usually sent in packets that pass through routes across the Internet.



Rodney