Hosts on a switch cannot communicate to each other if they use different VLANs. The traditional way in creating a communication line between different VLANs is by adding a router on a stick and creating sub-interfaces to connect both VLANs. Although this method works perfectly, 
router on a stick can have its drawbacks such as loading the router processor and acting as a single point of failure.
Another way to create inter-VLAN communication is by using Switch Virtual Interface (SVI) that can be implemented on switches which have an internal route processor or called as Route Switch Module (RSM). SVI is already implemented for VLAN 1 by default.
MLS can be configured for any VLAN in a L3 Switch in order to communicate with ther VLANs.
Before creating the process, make sure the ip routing is already on by using the command:
(config)#ip routing
The first one to do is to create the VLAN and configure the ports on the proper VLANs with the command:
(config)#int fa
(config-if)#switchport mode access
(config-if)#swichport access vlan //VLANs will be created
To create the SVI is simple:
(config>#int vlan // to access the vlan interface
(config-if)#ip address // to create an ip address for the VLAN SVI
Note that the line protocol should be running and show ip config can be done to show the SVI.
The process above should be done to all VLANs at the switch if it wants to communicate. #show ip route will show the route of the switch and it can be seen that the switch has route to the different VLANs.
In order for the host to communicate with other host in different VLANs, make sure that the gateway of the hosts is the IP address of the SVI.
HOST(config)#ip route 0.0.0.0 0.0.0.0.
After this, the hosts should be able to communicate with other hosts.
If the L3 Switch must reach another router, the port interface of the switch must be changed to routed port so that it will be able to route traffic. The command is simple which is "(config-if)#no switchport mode access" on a interface, because if the port is in the switchport access mode, then the port acts as a switch port. After that set the IP address of the port by "(config-if)#ip address ".
-- 22 November 2010 --
router on a stick can have its drawbacks such as loading the router processor and acting as a single point of failure.Another way to create inter-VLAN communication is by using Switch Virtual Interface (SVI) that can be implemented on switches which have an internal route processor or called as Route Switch Module (RSM). SVI is already implemented for VLAN 1 by default.
MLS can be configured for any VLAN in a L3 Switch in order to communicate with ther VLANs.
Before creating the process, make sure the ip routing is already on by using the command:
(config)#ip routing
The first one to do is to create the VLAN and configure the ports on the proper VLANs with the command:
(config)#int fa
(config-if)#switchport mode access
(config-if)#swichport access vlan
To create the SVI is simple:
(config>#int vlan
(config-if)#ip address
Note that the line protocol should be running and show ip config can be done to show the SVI.
The process above should be done to all VLANs at the switch if it wants to communicate. #show ip route will show the route of the switch and it can be seen that the switch has route to the different VLANs.
In order for the host to communicate with other host in different VLANs, make sure that the gateway of the hosts is the IP address of the SVI.
HOST(config)#ip route 0.0.0.0 0.0.0.0
After this, the hosts should be able to communicate with other hosts.
If the L3 Switch must reach another router, the port interface of the switch must be changed to routed port so that it will be able to route traffic. The command is simple which is "(config-if)#no switchport mode access" on a interface, because if the port is in the switchport access mode, then the port acts as a switch port. After that set the IP address of the port by "(config-if)#ip address
-- 22 November 2010 --
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