CCNA: General Switching/Creating Ports

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Description:

These commands are for general switching and creating ports in a Cisco router/switch.

To configure a single port

Router>enable
Router#config t
Router(config)#interface f0/5
Router(config-if)#

To configure multiple ports at once

Switch(config)#interface range FastEthernet0/3 – 4, 24

Interface Options:

Switch>enable
Switch#config term
Switch(config)#interface f0/5
Switch(config-if)#speed 100 # sets speed
Switch(config-if)#duplex full # sets duplex mode - must match on both sides! Auto only recommended for Gigabit
Switch(config-if)#description Web Server
Switch(config-if)#no shutdown # all ports are shut down by default, you must turn them on by running this!
Switch(config-int)#ip address # the most common command, sets an ipv4 address
Switch(config-if)#ip address 10.0.1.3 255.255.255.0 secondary # You can set a secondary IP
Switch(config-if)#bandwidth # Doesn't change the speed, just how routing protocols view an interface.
Switch(config-if)#delay # Doesn't change the speed, just how routing protocols view an interface.

To create an access port:

#NOTE: All ports should be access ports by default, we still configure them to make sure. Switch to switch or switch to router should be trunk ports.

Switch(config)#interface f0/5
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 100
Switch(config-if)#switchport voice vlan 150

To create a trunk port:

Switch(config)#int fa0/0
Switch(config-if)#switchport mode trunk
Switch(config-if)#switchport nonegotiate # recommended to disable DTP
Switch(config-if)#switchport trunk native vlan 99 # You have to change the native vlan from within an interface. By default this is VLAN1 and should be changed for security.
Switch(config-if)#switchport trunk allowed vlan 100 # this only allows VLAN 100
Switch(config-if)#switchport trunk allowed vlan 10, 20-30 # over-rides it to include vlans 10 and 20-30
Switch(config-if)#switchport trunk allowed vlan add 12 # this is the correct way to add a new VLAN without overridding
Switch(config-if)#switchport trunk encapsulation dot1q # uses the open standard 802.1q for encapsulation (most common)
Switch(config-if)#end

To create a loopback port:

Switch(config)#interface loopback 0
Switch(config-if)#ip address 192.168.20.1 255.255.255.0
Switch(config-if)#exit

Show Commands:

show ip interfaces brief # normally typed: show ip int bri
show interfaces

 

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