LAN Switching, Types of switch & Password Breaking of switch

Ethernet switches are used in LAN to create Ethernet n/ws. Switches forward the traffic on the basis of MAC address. Switches maintain a Mac Address table in which mac addresses and port no.s are used to perform switching decision. Working of bridge and switch is slimier to each other.
                             Classification of switches

Switches are classified according to the following criteria : - Types of switches based on working

(1) Store & Forward :-- This switch receives entire frame then perform error checking and start forwarding data to the destination. 

(2) Cut through :-- This switch starts forwarding frame as soon as first six bytes of the frame are received.

(3) Fragment-free :-- This switch receives 64 bytes of the frame, perform error checking and then start forwarding data. 

 (4) Adaptive cut-through :--It changes its mode according the condition. If it see there are errors in many frames then it will change to Store & Forward mode from Cut through or Fragment-free.

Types of switches based on management

(1) Manageable switches

(2) Non-Manageable switches

Types of switches based on OSI layer

(1) Layer 2 switches (only switching)

(2) Layer 3 switches (switching & routing)

Types of switches based on command mode (only in Cisco)

(1) IOS based

(2) CLI based

Type of switches based on hierarchical model

(1) Core layer switches

(2) Distribution layer switches

(3) Access layer switches

Qualities of switch

- No. of ports

- Speed of ports

- Type of media

- Switching or wire speed or throughput

Basic Switch Administration

IOS based switches are similar to the routers. We can perform following function on switches in a similar manner as performed on router.

(1) Access switch using console

(2) Commands to enter & exit from different mode

(3) Commands to configure passwords

(4) Manage configuration

(5) Backup IOS and configuration

(6) Configuring and resolving hostnames

(7) Managing telnet

(8) Configuring CDP

(9) Configuring time clock

(10) Configuring Banners

(11) Command line shortcuts and editing shortcuts

(12) Managing history

(13) Configure logging

(14) Boot system commands

 Following function and options are not similar in router and switch.

(1) Default hostname is ‘Switch’

(2) Auxiliary port is not present

(3) VTY ports are mostly 0 to 15

(4) By default interfaces are enabled

(5) IP address cannot be assign to interfaces

(6) Routing configuration mode is not present

(7) Interface no. starts from 1

(8) Web access is by default enabled

(9) Configuration registry is not present in similar manner

(10) Flash memory may contain multiple files and startup-configuration is also saved in flash.

                           Configuring IP and Gateway on switch

We can configure IP address on switch for web access or telnet IP address is required for the administration of the switch. If we have to access switch from remote n/w then we will configure default gateway in addition to IP address.

IP address is assigned to the logical interface of switch with following command:-

Switch(config)#interface vlan 1

Switch(config)#IP address <ip> <mask>

Switch(config)#no sh

Switch(config)#exit

Configuring Gateway

Switch(config)#ip default-gateway <ip>

Switch(config)#exit

Breaking Switch Password

(1) Power off switch press mode button present in front of switch then power on the  switch.

(2) Keep mode button press until ‘Switch:’ prompt appears on console.

(3) In switch monitor mode, type following commands: -

      flash_init

      load_helper

      rename flash:config.text flash:<anyname>

      dir flash:

      boot

(4) After booting switch will prompt to enter in initial configuration dialog. Enter ‘no’ here and type.

                                         Switch>enable

                   Rename flash:<anyname> Flash:config.text    

                   Configure memory

Change password and save config. Then copy run start_config.

                       Cisco Hierarchal Model

When we want to create a large sized LAN network then we may face following problem if we are going design the network in flat model.  

(1) High latency

(2) Conjunction between switches

(3) Large broadcast domain

Cisco hierarchal model recommends three layer design of the network

(i) Core layer

(ii) Distribution layer

(iii) Access layer

On each layer there are some rules which we have to follow

(1) Highest performance devices are connected on Core layer

(2) Resources should be placed on Core layer

(3) Polices should not be applied on core layer

(4) On distribution layer, we can implement policies

(5) Distribution and Core devices should be connected with high-speed links.

(6) Access layer devices are basic devices and may be non manageable.

(Hierarchal model)

After using hierarchal model the most of LAN problem will be solve but one problem still remain same that is all pc s will be in single broadcast domain. We have to implement following solution for this problem.

(1) Physical Segmentation

(2) Logical Segmentation

            VLAN

            Trunking

            VTP

            Inter VLAN

            Pruning

Logical Segmentation of Network

To perform logical segmentation, we have to create VLAN in the network. With the help of VLAN, we can logically divide the broadcast domain of the network.

Posted in: CCNA