How To Create A VLAN on A Cisco Switch?

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monica
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What Is A VLAN?
When you purchase a physical switch, all the ports on that switch are part of one big default LAN.  This LAN is also a VLAN because without any additional configuration the switch software sees all the switch-ports as part of that one default LAN.  When you create a VLAN on a physical switch, it creates another LAN group/VLAN that  the switch-ports can join. A VLAN takes a larger network and divides it into smaller networks.  VLANS are logical (logical meaning the way the software on the switch see it) network partitions on a switch.  It segments a switch into arbitrary broadcast domains.  Limiting the scope of the broadcast enhances the performance of the switch.  A VLAN is a virtual local area network.

Can One VLAN Talk To Another VLAN?
Not via Layer 2 but if the packet goes to a router then it can reach another VLAN.  Layer 3 switches can route packets to other VLANS on the same switch.

How Many IP's Can Fit Onto One VLAN?
You can put as many as you want but if the point is to keep your traffic tight you will want to keep your networks no larger than they have to be.  This is done by using classless networking, where you can split up these large networks into smaller networks.

RFC1918 Name                        IP Range                                                    #of addresses

CLASS A 24-bit block       10.0.0.0 – 10.255.255.255             16,777,216

CLASS B 20-bit block        172.16.0.0 – 172.31.255.255         1,048,576

CLASS C 16-bit block         192.168.0.0 – 192.168.255.255    65,536

Do All Enterprises Use VLANS?
Yes.  They are using VLANS on physical switches or virtual switches such as VMware vswitch.

About Cisco VLANS
Cisco physical switches come with a default VLAN called VLAN 1 that cannot be deleted.  VLANS 1002-1005 are also default VLANS.

How To Create A VLAN?
en|show vlan

(config)vlan 100

(config-vlan)name BUTTER |state active|end

(config-if) int fa0/2 |Switchport access vlan 100

do show int fa0/5 switchport (shows port details)

switchport mode access (changes mode into administrative mode static access)

You can assign multiple ports to a vlan using the config-if-range command

Security Measures - move all switchports out of vlan1
Category
Routers and Switches
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