Tag - Ip Networks

Autonomous System (AS)

1. What is an Autonomous System?

An Autonomous System (AS) is a group of IP networks operated by one or more network operator/s which has a single and clearly defined external routing policy. Exterior routing protocols are used to exchange routing information between Autonomous Systems.

2.When should an Autonomous System be created?

An AS needs to be created if a network connects to more than one AS with different routing policies. Some common examples of Autonomous Systems are networks connected to two or more upstream service providers or exchange points, networks peering locally at exchange points.

3.What is an Autonomous System Number?

A public AS has a globally unique number, an Autonomous System number (ASN), associated with it; this number is used in both the exchange of exterior routing information (between neighboring Autonomous Systems), and as an identifier of the AS itself.

There are two types of Autonomous System numbers; Public AS numbers and Private AS numbers.

4.When is a Public Autonomous System number required?

A Public AS number is required only when an AS is exchanging routing information with other Autonomous Systems on the public Internet. That is, all routes originating from an AS is visible on the Internet.

5. Am I eligible for a Public Autonomous System Number?

An organisation is eligible for an ASN assignment if it:

  • is multihomed (this includes organisations connected to a public Internet Exchange Point); and
  • has a single, clearly defined routing policy that is different from its providers’ routing policies.

An organisation will also be eligible if it can demonstrate that it will meet the above criteria upon receiving an ASN (or within a reasonably short time thereafter).

6. When can I use a Private Autonomous System number?

A Private AS number should be used if an AS is only required to communicate via BGP with a single provider. As the routing policy between the AS and the provider will not be visible in the Internet, a Private AS Number can be used for this purpose.

The IANA has reserved AS64512 through to AS65535 to be used as private ASNs.

7. I plan to change my upstream providers – can I take my ASN with me?

This depends on how you received that ASN. If you got it directly from APNIC or an NIR, then it is portable and you can take it with you to whichever providers you choose (subject to the agreement you signed with APNIC or the NIR).

However if got your ASN from an LIR, you can only use it while you continue to receive connectivity from the LIR. In other words, if you decide to no longer use that LIR as one of your upstream providers, then you will have to return the ASN.


IP Addressing

IP address is a unique identifier of a computer on TCP/IP networks and on the internet.  Every computer requires a unique IP address to be a part of the internet and the IP address is provided by the internet service providers.  Every IP address consists of the 32 bits and a binary system of 0s and 1s.  The binary number system consist of only two types of digits 0 and 1. It is easier for us to remember the decimal numbers rather than the binary number system such as 011001101. On a same network segment, all the IP address share the same network address.

There are five classes of the IP addresses such as A, B, C, D and E and only 3 classes are in the use. Class D IP addresses are reserved for the multicast group ant cannot be assigned to hosts and the E class IP addresses are the experimental addresses and cannot be assigned to the people. Every IP address consists of 4 octets and 32 bits.  Every participating host and the devices on a network such as servers, routers, switches, DNS, DHCP, gateway, web server, internet fax server and printer have their own unique addresses within the scope of the network.

TCP/IP protocols are installed by default with the Windows based operating systems. After the TCP/IP protocols are successfully installed you need to configure them through the Properties Tab of the Local Area Connection.

IP Addresses Classes

Class A

The binary address for the class A starts with 0. The range of the IP addresses in the class A is between 1 to 126 and the default subnet mask of the class A is  Class A supports 16 million hosts on each of 125 networks.  An example of the class A is  Class A is used for the large networks with many network devices.

Class B

The binary address for the class B starts with 10. The range of the IP address in the class B is between 128 to 191 and the default subnet mast for the class B is  Class B supports 65,000 on each of 16,000 networks. An example of the class B address is  Class B addresses scheme is used for the medium sized networks.

Class C

The binary address for the class C starts with 110. The range of the IP addresses in the class C is between 192 to 223 and the default subnet mask for the class C is 255.255.255.  Class C hosts 254 hosts on each of 2 million networks.  An example of the Class C IP address is  Class C is used for the small networks with less then 256 devices and nodes in a network.

Class D

The binary addresses for the class D starts with 1110 and the IP addresses range can be between 224 to 239.  An example of the class D IP address is

Class E

The binary address can starts with 1111 and the decimal can be anywhere from 240 to 255.  An example of the class E IP address is

It is very important to know that all the computers in the same network segment should have the IP addresses for the same class i.e. form A, B or C

IP Addressing

IP Addressing Tips          

  • A Network ID cannot be All 0s
  • A host ID cannot be All 1 because this represents a broadcast address for the local network.
  • Each host must have a unique host portion of the IP address.
  • All hosts on the same network segment should have the same network id.
  • A host address cannot be 127 because 127 has been reserved for the loop back functionalities.

CCNP Dumps


Cisco CCNP Certification Exams Training Materials

It is well known that Cisco CCNP certification training is experiencing a great demand in IT industry area. In recent years, the CCNP certification has become a global standard for many successful IT companies.

CCNP Exam Code = 642-902

Title = Implementation Cisco IP Routing (Route) Practice Test

Total Question = 484

CCNP Dumps Format = PDF

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About CCNP

CCNP® (Cisco Certified Network Professional) Routing and Switching certification indicates advanced knowledge of networks. It is the second stage of the Network Installation and Support track, and it teaches the installation, configuration, and operation of LAN, WAN, and dial access services for medium-to-large networks with multiple protocols


Valid CCNA certification or any CCIE Certification.


The three required exams may be taken in any order:
642-902 ROUTE, Implementing Cisco IP Routing
642-813 SWITCH, Implementing Cisco Switched Networks
642-832 TSHOOT, Troubleshooting and Maintaining Cisco IP Networks

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