Hubs

Hubs are used to build a LAN by connecting different computers in a star/hierarchal network topology, the most common type on LANs now a day. A hub is a very simple (or dumb) device, once it gets bits of data sent from computer A to B, it does not check the destination, instead, it forwards that signal to all other computers (B, C, D…) within the network. B will then pick it up while other nodes discard it. This amplifies that the traffic is shared.

There are mainly two types of hubs:

1. Passive: The signal is forwarded as it is (so it doesn’t need power supply).

2. Active: The signal is amplified, so they work as repeaters. In fact they have been called multiport repeaters. (use power supply)

Hubs can be connected to other hubs using an uplink port to extend the network.

OSI Model: Hubs work on the physical layer (lowest layer). That’s the reason they can’t deal with addressing or data filtering.

MAC Address

In computer networking, the Media Access Control (MAC) address is every bit as important as an IP address. Learn in this article how MAC addresses work and how to find the MAC addresses being used by a computer.

What Is a MAC Address?

The MAC address is a unique value associated with a network adapter. MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN.

MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following formats:

MM:MM:MM:SS:SS:SS

MMMM-MMSS-SSSS

The first half (24 BITS) of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half (24 MORE BITS) of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,

00:A0:C9:14:C8:29

The prefix

00A0C9

indicates the manufacturer is Intel Corporation.

Why MAC Addresses?

Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.

MAC vs. IP Addressing

Whereas MAC addressing works at the data link layer, IP addressing functions at the network layer (layer 3). It's a slight oversimplification, but one can think of IP addressing as supporting the software implementation and MAC addresses as supporting the hardware implementation of the network stack. The MAC address generally remains fixed and follows the network device, but the IP address changes as the network device moves from one network to another.

IP networks maintain a mapping (association) between the IP address of a device and its MAC address. This mapping is known as the ARP cache or ARP table. ARP, the Address Resolution Protocol, supports the logic for obtaining this mapping and keeping the cache up to date.
DHCP also usually relies on MAC addresses to manage the unique assignment of IP addresses to devices.
The method used to find a MAC address depends on the type of network device involved. All popular network operating systems contain utility programs that allow one to find (and sometimes change) MAC address settings.

Find a MAC Address in Windows

In Windows 95, Windows 98 and Windows ME, the winipcfg utility displays MAC addresses. In Windows NT and any newer versions of Windows, the ipconfig utility (using the /all option) can also be used.

OSI Seven-Layer Mode

In the 1980s, the European-dominated International Standards Organization (ISO), began to develop its Open Systems Interconnection (OSI) networking suite.

In this model, a networking system is divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacts directly only with the layer immediately beneath it, and provides facilities for use by the layer above it. Protocols enable an entity in one host to interact with a corresponding entity at the same layer in a remote host.

The seven layers of the OSI Basic Reference Model are (from bottom to top):

1. The Physical Layer describes the physical properties of the various communications media, as well as the electrical properties and interpretation of the exchanged signals. Ex: this layer defines the size of Ethernet coaxial cable, the type of BNC connector used, and the termination method.
2. The Data Link Layer describes the logical organization of data bits transmitted on a particular medium. Ex: this layer defines the framing, addressing and check-summing of Ethernet packets.
3. The Network Layer describes how a series of exchanges over various data links can deliver data between any two nodes in a network. Ex: this layer defines the addressing and routing structure of the Internet.
4. The Transport Layer describes the quality and nature of the data delivery. Ex: this layer defines if and how retransmissions will be used to ensure data delivery.
5. The Session Layer describes the organization of data sequences larger than the packets handled by lower layers. Ex: this layer describes how request and reply packets are paired in a remote procedure call.
6. The Presentation Layer describes the syntax of data being transferred. Ex: this layer describes how floating point numbers can be exchanged between hosts with different math formats.
7. The Application Layer describes how real work actually gets done. Ex: this layer would implement file system operations.

What is ping?

 Ping is a program that sends a series of packets over a network or the Internet to a specific computer in order to generate a response from that computer. The other computer responds with an acknowledgment that it received the packets. Ping was created to verify whether a specific computer on a network or the Internet exists and is connected.

Some have claimed that the word "ping" is actually an acronym for "Packet Internet (or Inter-Network) Groper", deliberately contrived to play on the fact that pinging with a computer is similar to what submariners do with sonar. Both the computer and the submarine's sonar send out a "ping", in the form of either a series of packets or a brief burst of sound. The ping "bounces" off the target and then returns to let you know the target is there.

Ping is both a noun and a verb, e.g., "Ping that computer", or "the router didn't return a ping".
Ping is built into almost every network-capable operating system. To ping a computer, go to a command prompt and enter ping , a space, and then the network or Internet address you wish to contact. For example, enter the following at a Windows XP command prompt:

ping 66.218.71.198

 

You should get a response similar to this:

pinging 66.218.71.198 with 32 bytes of data: 

Reply from 66.218.71.198: bytes=32 time<1ms TTL=127 

Reply from 66.218.71.198: bytes=32 time<1ms TTL=127 

Reply from 66.218.71.198: bytes=32 time<1ms TTL=127 

Reply from 66.218.71.198: bytes=32 time<1ms TTL=127 

ping statistics for 66.218.71.198: 

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), 

Approximate round trip times in milli-seconds: 

Minimum = 0ms, Maximum = 0ms, Average = 0ms

What is IP?

IP stands for Internet Protocol. All devices such as PCs, website servers, switches and routers have an IP address to communicate over the internet. Think of an IP address as a postcode or zip code, without the postcode or zip code, we cannot receive our mail through the postal system. An Internet Protocol address is a 32-bit number, which looks similar to 217.17.21.17 (each 8 bit number can start from 1-255). I do not want to go into to much detail, but hope you get the idea that all devices on the internet will have an IP address.

What is ICMP?

ICMP stands for Internet Control Message Protocol. ICMP was created to send test messages across an IP network. Sending these messages would let you know if a device like PCs, website servers, switches and routers are contactable over an IP network. Ping uses ICMP to contact other devices on the IP network.

The nature of ping.

Many people in the IT world will recognise ping as a network utility to test whether or not a device such as a router, server or switch is contactable. The way this works is the computer or device will generate an ICMP packet that is sent over the local network or internet. The ICMP packet will find its way across the network by having a source and destination IP address. When the device receives this information it then sends a reply saying “yes, I am here”. As I work for an ISP (Internet Service Provider) myself this is an essential tool to help do my job. Ping is used a lot in IT and network troubleshooting.

FSMO roles

FSMO roles means flixible singal master opreation. means all these master role can be shiftt or change.ther are five roles.when u installed the first domain in the forest they all five roles are installed on that, but due to every roles has its own responsibleities so that ther is a risk to slowe down the server in all that five roles first two roles are called forest wide roles that are 1. schema master role. 2. is domain naming master role. these roles should be on the first domain of the forest.

In a forest, there are five FSMO roles that are assigned to one or more domain controllers. The five FSMO roles are:

• Schema Master:The schema master domain controller controls all updates and modifications to the schema. Once the Schema update is complete, it is replicated from the schema master to all other DCs in the directory. To update the schema of a forest, you must have access to the schema master. There can be only one schema master in the whole forest.

• Domain naming master:The domain naming master domain controller controls the addition or removal of domains in the forest. This DC is the only one that can add or remove a domain from the directory. It can also add or remove cross references to domains in external directories. There can be only one domain naming master in the whole forest.

• Infrastructure Master:When an object in one domain is referenced by another object in another domain, it represents the reference by the GUID, the SID (for references to security principals), and the DN of the object being referenced. The infrastructure FSMO role holder is the DC responsible for updating an object's SID and distinguished name in a cross-domain object reference. At any one time, there can be only one domain controller acting as the infrastructure master in each domain.

Note: The Infrastructure Master (IM) role should be held by a domain controller that is not a Global Catalog server (GC). If the Infrastructure Master runs on a Global Catalog server it will stop updating object information because it does not contain any references to objects that it does not hold. This is because a Global Catalog server holds a partial replica of every object in the forest. As a result, cross-domain object references in that domain will not be updated and a warning to that effect will be logged on that DC's event log. If all the domain controllers in a domain also host the global catalog, all the domain controllers have the current data, and it is not important which domain controller holds the infrastructure master role.

• Relative ID (RID) Master:The RID master is responsible for processing RID pool requests from all domain controllers in a particular domain. When a DC creates a security principal object such as a user or group, it attaches a unique Security ID (SID) to the object. This SID consists of a domain SID (the same for all SIDs created in a domain), and a relative ID (RID) that is unique for each security principal SID created in a domain.  Each DC in a domain is allocated a pool of RIDs that it is allowed to assign to the security principals it creates. When a DC's allocated RID pool falls below a threshold, that DC issues a request for additional RIDs to the domain's RID master. The domain RID master responds to the request by retrieving RIDs from the domain's unallocated RID pool and assigns them to the pool of the requesting DC. At any one time, there can be only one domain controller acting as the RID master in the domain.

What Are Forests?

At its highest level, a forest is a single instance of Active Directory. Therefore, a forest is synonymous with Active Directory, meaning that the set of all directory partitions in a particular Active Directory instance (which includes all domain, configuration, schema and optional application information) makes up a forest. This means that when you have multiple forests in an enterprise they will, by default, act separately from each other as if they were the only directory service in your organization.
This behavior, however, is easily be modified so that multiple forests can share Active Directory responsibilities across an enterprise. This is done by creating external or forest trust relationships between the forests. In this way, each forest can be connected with every other forest to form a collaborative directory service solution for any enterprise with business needs that include multiple forest collaboration.
Forests can also be defined as:

• Collections of Domain Containers that Trust Each Other
• Units of Replication
• Security Boundaries
• Units of Delegation

 Forest functionality

Forest functionality enables features across all the domains within your forest. Three forest functional levels are available: 

•  Windows 2000 (default)
•  Windows Server 2003 interim, and
• Windows Server 2003 .

By default, forests operate at the Windows 2000 functional level. You can raise the forest functional level to Windows Server 2003 .

To install Active Directory on Windows Server 2003

     1.    Click Start, click Run, type dcpromo, and then click OK.

2.    On the first page of the Active Directory Installation Wizard, click Next.

Note:

If this is the first time you have installed Active Directory, you can click Active Directory Help to learn more about Active Directory before clicking Next.

3.    On the next page of the Active Directory Installation Wizard, click Next.

4.    On the Domain Controller Type page, click Domain Controller for a new domain, and then click Next.

5.    On the Create New Domain page, click Domain in a new forest, and then click Next.

6.    On the New Domain Name page, in the Full DNS name for new domain box, type corp.contoso.com, and then click Next.

7.    On the Database and Log Folders page, accept the defaults in the Database folder box and the Log folder box, and then click Next.

8.    On the Shared System Volume page, accept the default in the Folder location box, and then click Next.

9.    On the DNS Registration Diagnostics page, click Install and configure the DNS server on this computer and set this computer to use this DNS server as its preferred DNS Server, and then click Next.

10. On the Permissions page, click Permissions compatible only with Windows 2000 or Windows Server 2003 operating systems, and then click Next.

11. On the Directory Services Restore Mode Administrator Password page, enter a password in the Restore Mode Password box, retype the password to confirm it in the Confirm password box, and then click Next.

Note:

Consult your organization's security policy to ensure that the password you select meets your organization's security requirements.

12. On the Summary page, confirm the information is correct, and then click Next.

13. When prompted to restart the computer, click Restart now.

14. After the computer restarts, log on to CONT-CA01 as a member of the Administrators group.