width available on that link is only 10 Mbps. In contrast, when each VLAN has its own Chapter 4: VLANs E 0/0 Trunk Port 8 Port 9 Port 10 Port 11 Port 12 Port 13 Port 14 Port 15 VLAN 20 VLAN 30 VLAN 40 VLAN 10 VLAN 10 VLAN 20 Port 0 Port 1 Port 2 Port 3 Port 4 Port 5 Port 6 Port 7 Figure 4-5. Router on a stick link, each VLAN has 10 Mbps to itself. Also, don't forget that the router is passing traffic between VLANs, SO chances are each frame will be seen twice on the same link-once to get to the router, and once to get back to the destination VLAN. Using a switch with a router is not very common anymore because most vendors offer switches with layer-3 functionality built-in. Figure 4-6 shows conceptually how the same design would be accomplished with a layer-3 switch. Because the switch contains the router, no external links are required. With a layer-3 switch, every port can be dedicated to devices or trunks to other switches. Port 8 Port 9 Port 10 Port 11 Port 12 Port 13 Port 14 Port 15 VLAN 20 VLAN 30 VLAN 40 VLAN 10 VLAN 10 VLAN 20 Port 0 Port 1 Port 2 Port 3 Port 4 Port 5 Port 6 Port 7 Figure 4-6. Layer-3 switch Configuring VLANs VLANs are typically configured via the CatOS or IOS command-line interpreter (CLI), like any other feature. However, some IOS models, such as the 2950 and 3550 switches, have a configurable VLAN database with its own configuration mode and commands. This can be a challenge for the uninitiated, especially because the config- uration for this database is completely separate from the configuration for the rest the switch. Even a write erase followed by a reload will not clear the VLAN data- base on these switches. Configuring through the VLAN database is a throwback to Configuring VLANs older models that offered no other way to manage VLANs. All newer switches (including those with a VLAN database) offer the option of configuring the VLANs through the normal IOS CLI. Switches like the 6500, when running in native IOS mode, only support IOS commands for switch configuration. Cisco recomm