Cisco Networking

CCNP SWITCH 300-115:

Here I’m  going to take you through the fundamentals of Cisco switching technology. All the technologies covered in Cisco CCNP Switch Curriculum.

What is a network Switch?

A network switch is a multiport device that uses hardware addresses (Mac-Address) to process and forward data at the data link layer (layer 2) of the OSI model. Some switches can also process data at the network layer (layer 3) by additionally incorporating routing functionality. Such switches are commonly known as layer-3 switches or multilayer switches.

A network switch can be deployed in the following ways:

Access Layer:
The access layer Switch is responsible for providing end user devices with a connection to network resources.The access layer, which is the lowest level of the Cisco three tier network model, ensures that packets are delivered to end user devices. you can find Switches like Cisco 2950, 2960 models at the access layer.

Distribution Layer:
The Distribution layer Switch normally should be a Layer 3 or Multilayer Switch and this is where access-lists, QoS, and routing decisions should occur.you can find Switches like Cisco 3550, 3560, and 3750 models at the distribution  layer.

Core Layer:
The Core is the “backbone.” Its job is simply to move packets from point A to point B as fast as possible and with the least possible manipulation. Typically the core connects enterprise LANs to the edge routers or firewalls that connect them to the internet. You may likely see 3750 and 3850 Switches at the core layer. However you may need to collapse some of these layers into one single switch, for example you may have a 3750 or 3850 switch operating both as a core and distribution layer switch. it all depends on your environment and your budget.

What is a Vlan?

Vlan (which stands for Virtual Local Area Network) is the logical grouping of network users and resources to administratively defined ports on a Switch.

Benefits Of Vlan


1. Security – In a VLAN network environment, with multiple broadcast domains, network administrators have control over each port and user. A malicious user can no longer just plug their workstation into any switch port and sniff the network traffic using a packet sniffer. The network administrator controls each port and whatever resources it is allowed to use.

E.g, – Companies may want VLANs set up for departments that are heavy network users (such as multimedia or engineering), or a VLAN across departments that is dedicated to specific types of employees (such as managers or sales people).

2. Broadcast Control – Vlan helps to control network traffics thereby minimizing broadcast messages on the network.

3. Vlan simplifies network management – Security policies can be applied to various Vlans instead of individual users.

 

Implementing Vlan On A Switch

Switch>en
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#vlan 2
Switch(config-vlan)#name SALES
Switch(config-vlan)#vlan 3
Switch(config-vlan)#name ADMIN
Switch(config-vlan)#vlan 4
Switch(config-vlan)#name FINANCE
Switch(config-vlan)#exit
Switch(config)#

How To Assign Switchports To A Vlan


Switch(config)#
Switch(config)#int f0/1
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 2
Switch(config-if)#exit
Switch(config)#int f0/2
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 3
Switch(config-if)#exit
Switch(config)#int f0/3
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 4
Switch(config-if)#end
Switch#
%SYS-5-CONFIG_I: Configured from console by console

Switch#copy run start

Vlan Verification Commands


Switch#show vlan or show vlan brief


Switch#

Switchport Trunking


Trunk links are required to pass VLAN information between switches on the network. Switchport trunk means that all VLANs are allowed to pass through a trunk link.

To configure a trunk on a switch FastEthernet port, use the switchport mode trunk command.
This command puts the interface into permanent trunking mode and negotiates to convert the neighboring switch or links into trunk links.

Switch>en
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#int f0/2
Switch(config-if)#switchport mode trunk
Switch(config-if)#end
Switch# copy run start
Switch#