|  | 1.2 | Virtual LANs
| 1.2.4 | VLANs establish broadcast domains
VLANs are an effective mechanism for extending firewalls from the routers to the switch fabric and protecting the network against potentially dangerous broadcast problems. Additionally, VLANs maintain all of the performance benefits of switching. These firewalls are accomplished by assigning switch ports or users to specific VLAN groups both within single switches and across multiple connected switches. Broadcast traffic within one VLAN is not transmitted outside the VLAN. Conversely, adjacent ports do not receive any of the broadcast traffic generated from other VLANs. This type of configuration substantially reduces the overall broadcast traffic, frees bandwidth for real user traffic, and lowers the overall vulnerability of the network to broadcast storms. You can easily control the size of the broadcast domain by regulating the overall size of its VLANs, restricting the number of switch ports within a VLAN and restricting the number of users residing on these ports. The smaller the VLAN group, the smaller the number of users affected by broadcast traffic activity within the VLAN group.