Support
The Cisco 870 series routers support clients on both physical LANs and virtual LANs (VLANs). The routers can use the Dynamic Host Configuration Protocol (DHCP) to enable automatic assignment of IP configurations for nodes on these networks.
Figure 5-1 shows a typical deployment scenario with two physical LANs connected by the router and two VLANs.
Figure 5-1 Physical and Virtual LANs with DHCP Configured on the Cisco Router
DHCP
DHCP, which is described in RFC 2131, uses a client/server model for address allocation. As an administrator, you can configure your Cisco 800 series router to act as a DHCP server, providing IP address assignment and other TCP/IP-oriented configuration information to your workstations. DHCP frees you from having to manually assign an IP address to each client.
When you configure a DHCP server, you must configure the server properties, policies, and DHCP options.
Note Whenever you change server properties, you must reload the server with the configuration data from the Network Registrar database.
VLANs
The Cisco 870 series access routers support four Fast Ethernet ports on which you can configure VLANs.
VLANs enable networks to be segmented and formed into logical groups of users, regardless of the user’s physical location or LAN connection.
Configuration Tasks
Perform the following tasks to configure this network scenario:
•Configure DHCP
•Configure VLANs
Note The procedures in this chapter assume you have already configured basic router features as well as PPPoE or PPPoA with NAT. If you have not performed these configurations tasks, see Chapter 1 «Basic Router Configuration,» Chapter 3 «Configuring PPP over Ethernet with NAT,» and Chapter 4 «Configuring PPP over ATM with NAT» as appropriate for your router.
Configure DHCP
Perform these steps to configure your router for DHCP operation, beginning in global configuration mode:
Router(config)# ip domain name smallbiz.com