IPv6 Multicast Addresses

Important IPv6 multicast addresses in CCNA exam perspective

FF01::1    -    ALL NODES(NODE-LOCAL)
FF01::2    -    ALL ROUTERS (NODE-LOCAL)
FF02::1    -    ALL NODES (LINK-LOCAL)
FF02::2    -    ALL ROUTERS (LINK LOCAL)
FF02::5    -    OSPFv3 ROUTERS
FF02::6    -    OSPFv3 DESIGNATED ROUTERS
FF02::9    -     RIPng
FF02::A    -    EIGRP ROUTERS
FF02::B    -    MOBILE AGENTS
FF02::C    -    SSDP
FF02::D    -    ALL PIM ROUTERS
FF05::2     -   ALL ROUTERS (SITE LOCAL)
FF05::1:3  -   DHCP SERVERS/RELAY AGENTS

Computer Security 17514 Model Answer Summer 2015

What is MAC address? How to Find or Locate MAC address?

MAC address

MAC address stands for Media Access Controller Address. 

MAC address is also called as hardware address or Ethernet address or physical address of a computer (end entities/devices in network capable of sending and receiving bits). 

MAC address is of 48 bit and it is represented in hexadecimal notation. These 48 bits are grouped into 6 part. each part contains 8 bit, which is called as octet. two octets are separated by either a colon (:) or by hyphen (-).

Each computer that is going to connect on network must have an ethernet card (NIC card) and MAC address assigned to that card. MAC address is assigned to NIC card by the manufacturer of NIC card. 

As earlier discussed earlier MAC address is of 48 bit (6 octet), in which 24 bit (first 3 octet) represent manufacturer ID and remaining 24 bits (remaining or last 3 octet) represent the serial number of card manufactured by manufacturer.

Example

1. 1A-2B-3C-4D-5E-6F
2. 9F:7E:5D:3C:1B:2A

In First MAC address '1A-2B-3C' is Manufacturer ID and '4D-5E-6F' Serial Number of NIC card.

MAC address is used to communicate over Data Link Layer. It is also used to communicate over Local Area Network or broadcast network.

If NIC card or Ethernet card is available in computer but driver software for it is not installed then it cant work. It cant show you Local Area Connection icon. It can not show MAC address of it. It cannot connect computer over network. To make NIC card usable, it is must to install driver software. After successful installation of driver, Local Area Connection icon is visible and MAC address can be located.

In this article I am going to show some steps which gives you How to Locate MAC address of Computer. MAC address can be located using different methods. here I am going to tell you two ways of locating MAC address.

Method 1 using command prompt.

First of all you have to open command prompt. There are different ways of opening command prompt. 

Following are ways of opening command prompt.
 

1. Click on start, then click on run (which opens run wizard) and type cmd and press enter
2. Press windows+r to get run wizard. Now type cmd and press enter.
3. Click on start and type command prompt, command prompt icon is displayed. click on command prompt.
4. Another way is to start --> all programs --> accessories --> command prompt.

Command Prompt

From above method you will get command prompt Next you have locate MAC address so again there are two commands.

First command is the getmac command. This command is used to get MAC address of your computer. So you just have to enter getmac into command prompt and press enter. Result of this command show you physical address and transport name. The field under physical address is your MAC address.

getmac command

getmac command result

Second command is the ipconfig. This command shows windows IP configuration details on command prompt. You just has to type ipconfig /all in command prompt and press enter. Result similar to following result will appear. the result contains windows IP configuration and Ethernet adapter Local Area Connection. Just find the field physical address which will show you MAC address of your computer.

ipconfig /all command result

Second Method

Another way is to locate MAC address is find icon of local area connection on taskbar and click on that. find Open Network and Sharing Center and click on that.

Network Sharing center will appear. Now find Local Area connection or go to change adapter setting and the go to Local Area Connection.

Network and Sharing Center

Now Local Area Connection Status will appear. Here find details and click on it to view details of Local Area Connection.

Local Area Connection Status

Now Local Area Connection details will appear in that find physical address will appear. In front of physical address there is MAC address of system.

Network Connection Details

 These are the ways to find MAC address of computer systems. MAC address can be located using command prompt or by using Ethernet adapter details.

Bridge Networking Device

Bridge

Bridge is a network device which divides a big network into smaller sub networks called segments. These segments are not consider as a separate network. Rather two segments can acts as a part of a single network because of bridge.

Bridges operates at both layers of OSI reference model that are physical layer as well as data link layer. Bridge is intelligence device which takes decision whether to forward the incoming frame on other port or discard it. It can also learn physical address of connected hosts and maintain this record in table called as forwarding table.

A bridge is basically a simplified two-port switch connecting two network segments. It does not have VLAN functions.

When bridge receives traffic on its any port, it checks incoming traffic and decides whether to forward or discard it. This decision is based on MAC address and forwarding table. the forwarding table is used by bridge while making filtering decisions.

Bridge know the physical address (MAC address) of all stations connected to it by listening network. Most of the bridges have capabilities to listen network automatically. Some other bridges don't have automatic learning capability, so in that case user or administrator has to manually add MAC address entries of connected hosts in bridging table for making decision.

Bridge checks incoming frame on a specific port connecting network segment, it then reads the physical address of destination host contained in the frame and the compares address with a forwarding table.

When it finds a match. It discovers segment to which destination station belongs and it needs to sends the frame only to that segment. So the bridge simply forward the frame on particular port to which the destination host connected to segment.

If source and destination both remain on same segment then bridge does not forward the frame. If source and destination are on different segment then bridge has to forward frame to segment to which destination is connected.

If the recipient’s MAC address is not in the list, then the  bridge blocks the data from passing. Bridge can connect different network architecture like token ring and Ethernet.

Bridge Forwarding Table

Physical Address	Port Number
1A-2B-3C-4D-5E-6F	1
4B-3D-7F-2C-6F-A6	2
4D-5E-6F1A-2B-3C	1
3C-4D-1A-2B-5E-6F	2

Forwarding table shows that the hosts that are connected to port number 1 and 2 of bridge. All the systems connected to port 1 are part of one  segment and systems connected to port 2 are part of another segment.

Types of Bridge

1. Simple Bridge
2. Multi port Bridge
3. Source route bridge
4. Translation Bridge
5. Local Bridge
6. Remote Bridge

1. Simple Bridge

Simple bridge are most primitive & less expensive bridge. Simple bridge cannot learn physical address automatically. The user has to enter the address manually in the forwarding table.

Whenever a new station is connected its physical address must be added to forwarding table. If station is disconnected or removed, then its address entry must be deleted from the forwarding table. So the table must be modified to have proper communication.

The simple bridge links only LAN segments.

2. Multi port Bridge

The bridge must have minimum two port in order to connect two segments. To connect multiple segments of LAN, the bridge should have more than 2 ports. The multi port bridge is the bridge is used to connect more than two segments.

3. Source route bridge

The source of each packet defines the bridge and LANs through which the packet should go before reaching destination. Frame contains different addresses like source, destination and bridge address. The station do majority of work here. Bridges do not filter broadcast packets and collisions are not transferred. Source route bridge avoids looping problem, it is designed for token ring

4. Translation Bridge

Translation bridge is used to connects network segment running at different speed or using different protocols.

5. Local Bridge

Local Bridge is used to connect network segments of same type and same location.

6. Remote Bridge

Remote bridge is designed to connect two network segments at distant location using WAN link.

Bridge advantages

Bridge is self configuring device.
It is used to interconnect two LANs.
It can minimize traffic on a segment.
It filter traffic and increases throughout on a network.
Primitive bridges often inexpensive.
It isolate a busy network from a not so busy one

Bridge disadvantages

It is slower than repeater and hub.
It is more expensive than repeater.
Does not scale to extremely large network.
It gives an error in bridging of different MAC protocol.
Does not limit the scope of broadcasts.

Digital Subscriber Line

Digital Subscriber Line

As Internet access became widespread and increasingly important part of business, the telephone companies (the platform for internet connection) realize that they need to have a more competitive product. 

The telephone companies got solution is to start new digital services, offering over the local loop. They aim to provide Services with more bandwidth than standard telephone service (broadband).

A digital subscriber line (DSL) connection is a high-speed network connection. DSL connection is done by using the same wires as a regular telephone line. 

DSL provides dedicated point-to-point network access services. DSL service is provided using copper wire that is twisted-pair cable. The connection loop between a network service provider's central office and the customer.

DSL modems are connected to Digital Subscriber Line Access Multiplexer (DSLAM) through DSL circuits.

It creats three data channels: a high-speed downstream channel, a low-speed upstream channel, and a basic telephone service channel.

The DSLAM (the cloud) provides one of the main differences between DSL and cable modems.

Because cable-modem users generally share a network loop that runs through a neighborhood, adding users means lowering performance in many instances.

Asymmetric Digital Subscriber Line (ADSL) provides a dedicated connection from each user to the DSLAM. Therefore, users won't see a performance decrease as new users are added.

Customer premises must contain Network Interface device which is connected to DSL connection. The Network Interface device is closely connected to splitter, which separates channels (band).

A DSL Modem can be used to connect to a modem port defined in the Cloud using telephone wire.

Another device (such as a PC or a router) is connected to Ethernet port on the DSL Modem.

The DSL Modem acts like a bridge forwarding traffic from one port to the other port.

Computer Network and Types

Computer Network

          Computer Network is the collection of two or more computer systems that are interconnected to each other using transmission media for the purpose of communication.

        A computer network is a system for communication among two or more computers. Computer networks can be categorized by range (geography of network) and functional network relationship (based on component role).

Classification of Computer Network on the basis of Geographical area covered

1. LAN (Local Area Network)
2. MAN (Metropolitan Area Network)
3. WAN (Wide Area Network)
4. PAN (Personal Area Network)
5. CAN (Campus Area Network

NETWORK SCALE

sr. No.	Network Type	Area Covered
1	PAN	1 M to 10 M
2	LAN	10 M to 1 KM
3	CAN	1 KM to 3 KM
4	MAN	1 KM to 10 KM
5	WAN	100 KM to 1000 KM

Classification of Computer Network on the basis of Component Role

1. Client Server network relationship
2. Peer to Peer network relationship

IP Address classes and default subnet mask

       IP address is a logical address, whose length is 32 bits. These 32 bits split into four part. These four part called as 'octet'. An octet has 8 bits. IP address can be represented in binary as well as in dotted decimal notation.
ex. Decimal 192.168.10.4

Class	Range	Default Subnet mask
Class A	1-126	255.0.0.0
Class B	128-191	255.255.0.0
Class C	192-223	255.255.255.0
Class D	224-239	For Multicasting
Class E	240-254	For Future use

       Class A, class B and class C IP addresses are used for assigning to computer system. Class D is used for multitasking and Class E is reserve for future use.