The following is a summary of each topic in the chapter and some questions for your reflection.
What Did I Learn in this Module? (11.3.1)
• Static and Dynamic Addressing—With a static assignment, the network administrator must manually configure the network information for a host. At a minimum, this includes the host IPv4 address, subnet mask, and default gateway. Static assignment of addressing information can provide increased control of network resources, but it can be time consuming to enter the information on each host. When using static IPv4 addressing, it is important to maintain an accurate list of which IPv4 addresses are assigned to which devices.
IPv4 addresses can be assigned automatically using a protocol known as DHCP. DHCP is generally the preferred method of assigning IPv4 addresses to hosts on large networks because it reduces the burden on network support staff and virtually eliminates entry errors. Another benefit of DHCP is that an address is not permanently assigned to a host but is only leased for a period of time. If the host is powered down or taken off the network, the address is returned to the pool for reuse.
As you enter area with a wireless hotspot, your laptop DHCP client contacts the local DHCP server via a wireless connection. The DHCP server assigns an IPv4 address to your laptop. With home networks, the DHCP server may be located at the ISP and a host on the home network receives its IPv4 configuration directly from the ISP. Many home networks and small businesses use a wireless router and modem. In this case, the wireless router is both a DHCP client and a server.
• DHCPv4 Configuration—The DHCP server is configured with a range, or pool, of IPv4 addresses that can be assigned to DHCP clients. A client that needs an IPv4 address will send a DHCP Discover message which is a broadcast with a destination IPv4 address of 255.255.255.255 (32 ones) and a destination MAC address of FF-FF-FF-FF-FF-FF (48 ones). All hosts on the network will receive this broadcast DHCP frame, but only a DHCP server will reply. The server will respond with a DHCP Offer, suggesting an IPv4 address for the client. The host then sends a DHCP Request asking to use the suggested IPv4 address. The server responds with a DHCP Acknowledgment.
For most home and small business networks, a wireless router provides DHCP services to the local network clients. To configure a home wireless router, access its graphical web interface by opening the browser and entering the router default IPv4 address. The IPv4 address of 192.168.0.1 and subnet mask of 255.255.255.0 are the defaults for the internal router interface. This is the default gateway for all hosts on the local network and also the internal DHCP server IPv4 address. Most home wireless routers have DHCP Server enabled by default.
Have you manually entered an IPv4 address for all the devices on your home network? These are called static addresses. I did this for my home network, and I made a mistake when entering the address for my tablet. I had to redo it. Can you imagine having to do this for a huge corporate network with hundreds, or even thousands of devices? What other advantages are there to using DHCP for device addressing?