1. How to Configure a VLAN Cisco Router<br />VLANs help to organize large networks.<br />Configure a VLAN on a Cisco Router by using a sub interface. The sub interface commands allow you to specify that the interface should encapsulate frames according to the IEEE 802.1Q standard. You can also specify a VLAN number.<br />Instructions<br />1 <br />Use the name and password given to you by your system administrator to log in. <br />Log on the router and enter enable mode using the standard user name and password assigned to you by your system administrator. Enter an enable password if required.<br />2 <br />Identify which interface will have VLANs. <br />Identify which physical interface will connect to the switch and which VLAN number is in use. It is possible that more than one interface will connect to VLANs. Record each interface and the VLAN numbers that will connect to it. As an example, let's assume VLAN 25 and 26 will connect to interface Fastethernet 0/0 and VLAN 78 will connect to Fastethernet 0/1.<br />3. Enter configuration mode by typing quot;
configure terminalquot;
. The prompt will change from quot;
Router#quot;
to quot;
Router(config)#quot;
.<br />4. Create or edit a subinterface. Type quot;
interface fastethernet 0/0.1quot;
. The prompt will change to quot;
Router(config-subif)#quot;
. The quot;
1quot;
following a period after the interface number is the subinterface number. This command will create the subinterface if it does not exist or allow you to edit subinterface 1 if it does exist.<br />5. Configure the subinterface with IEEE 802.1Q encapsulation and enter one of the VLAN numbers. Use the command quot;
encapsulation dot1Q 25quot;
to set this subinterface to handle VLAN 25.<br />6 <br />The addresses for each VLAN will come from the network design. <br />Enter the IP address for this VLAN. Each router virtual interface will need a unique IP address as designed in your IP address layout. For example, enter the command quot;
ip address 192.168.1.254 255.255.255.0quot;
. Both the address and the mask should come from your IP address design.<br />7. Enter quot;
exitquot;
to return to the main configuration prompt of quot;
Router(config)#quot;
<br />8. Configure the remaining subinterfaces on all required physical interfaces. Use the same commands but substitute the VLAN numbers and IP address from your network plan. In this example, enter quot;
interface fastethernet 0/0.2quot;
, quot;
encapsulation dot1Q 26quot;
, quot;
ip address 192.168.26.254 255.255.255.0quot;
and quot;
exitquot;
to configure the second VLAN. The last VLAN in our example would be entered using the command quot;
interface fastethernet 0/1.1quot;
, quot;
encapsulation dot1Q 76quot;
, quot;
ip address 192.168.76.254 255.255.255.0quot;
, quot;
exitquot;
. When all information is entered type quot;
endquot;
to exit configuration mode.<br />9. Verify the configuration by typing quot;
show runquot;
at the router enable prompt of quot;
Router#quot;
. Make sure the commands were typed in correctly and the addresses and VLAN numbers match the numbers in your plan.<br />10 <br />Don't forget to save the configuration changes. <br />Save the configuration by entering the command quot;
copy running-config startup-configquot;
.<br />Tips & Warnings<br />The commands shown here are spelled out in long form so they may be more easily understood. A proficient Cisco operator would abbreviate the commands.<br />For example, quot;
configure terminalquot;
would be abbreviated to quot;
conf tquot;
; quot;
interface would be abbreviated to quot;
intquot;
; quot;
fastethernetquot;
would be abbreviated to quot;
fquot;
; quot;
running-configquot;
would be abbreviated to quot;
runquot;
and quot;
startup-configquot;
would be abbreviated to quot;
startquot;
.<br />An alternative to the command quot;
copy run startquot;
is quot;
wr mequot;
, meaning quot;
write memory.quot;
<br />Remember that the changes you make take effect immediately.<br />Be certain you are editing the subinterface.<br />Deleted subinterfaces may not actually disappear until the the next reload.<br />Notes: If you wanna know more about guides and tips for Cisco equipment, you can visit: http://blog.router-switch.com/<br />