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The Gleasman Corporation has again hired you to help them with their networks in Nashville, Tennessee and Toronto, Canada. They’ve changed operating systems to Linux and are having some troubles with their DNS and DHCP configuration. Here are some details about the corporation: The Nashville site has a medium sized network of 170 users and 5 subnets using TCP/IP. That site also has Internet connectivity and maintains a web server. Both sites have Customer Service, Business, Inventory, and IT Departments. The Nashville site houses most of the management team, but Toronto has a vice president in charge of that location with an operations manager and supervisors for the Customer Service, Business, Inventory, and IT groups at that location. Nashville also has a Marketing Department. The IT Department is very inexperienced with some networking issues. Create a brief document for them about DNS and DHCP under Linux, including their purpose, configuration files, and troubleshooting tips. Provide them with some insight into how to they can incorporate the information your document provides into their system to make it better. Dynamic Host Configuration Protocol (DHCP) Dynamic Host Configuration Protocol (DHCP) is network protocol for automatically assigning TCP/IP information to client machines. Each DHCP client connects to the centrally-located DHCP server which returns that client's network configuration including IP address, gateway, and DNS servers. DHCP is useful for fast delivery of client network configuration. When configuring the client system, the administrator can choose DHCP and not have to enter an IP address, netmask, gateway, or DNS servers. The client retrieves this information from the DHCP server. DHCP is also useful if an administrator wants to change the IP addresses of a large number of systems. Instead of reconfiguring all the systems, he can just edit one DHCP configuration file on the server for the new set of IP address. If the DNS servers for an organization changes, the changes are made on the DHCP server, not on the DHCP clients. Once the network is restarted on the clients (or the clients are rebooted), the changes will take effect. Furthermore, if a laptop or any type of mobile computer is configured for DHCP, it can be moved from office to office without being reconfigured as long as each office has a DHCP server that allows it to connect to the network. Configuring a DHCP Server You can configure a DHCP server using the configuration file /etc/dhcpd.conf. DHCP also uses the file /var/lib/dhcp/dhcpd.leases to store the client lease database. Configuration File The first step in configuring a DHCP server is to create the configuration file that stores the network information for the clients. Global options can be declared for all clients, or options can be declared for each client system. The configuration file can contain any extra tabs or blank lines for easier formatting. The keywords are case-insensitive, and lines beginning with a hash mark (#) are considered comments. Two DNS update schemes are currently implemented — the ad-hoc DNS update mode and the interim DHCP-DNS interaction draft update mode. If and when these two are accepted as part of the IETF standards process, there will be a third mode — the standard DNS update method. The DHCP server must be configured to use one of the two current schemes. Version 3.0b2pl11 and previous version used the ad-hoc mode; however, it has been depreciated. If you want to keep the same behavior, add the following line to the top of the configuration file: ddns-update-style ad-hoc; To use the recommended mode, add the following line to the top of the configuration file: Ddns-update-style interim; Read the dhcpd.conf man page for details about the different modes. There are two types of statements in the configuration file: Parameters — state how to perform a task, whether to perform a task, or what network configuration options to send to the client. Declarations — describe the topology of the network, describe the clients, provide addresses for the clients, or apply a group of parameters to a group of declarations. Some parameters must start with the option keyword and are referred to as options. Options configure DHCP options; whereas, parameters configure values that are not optional or control how the DHCP server behaves. Parameters (including options) declared before a section enclosed in curly brackets ({ }) are considered global parameters. Global parameters apply to all the sections below it. The routers, subnet-mask, domain-name, domain-name-servers, and time-offset options are used for any host statements declared below it. You can declare a subnet. You must include a subnet declaration for every subnet in your network. If you do not, the DHCP server will fail to start. In this example, there are global options for every DHCP client in the subnet and a range declared. Clients are assigned an IP address within the range. subnet 192.168.1.0 netmask 255.255.255.0 { option routers 192.168.1.254; option subnet-mask 255.255.255.0; option domain-name "aiu.com"; option domain-name-servers 192.168.1.1; option time-offset -18000; # Eastern Standard Time range 192.168.1.10 192.168.1.100; } Subnet Declaration All subnets that share the same physical network should be declared within a shared-network declaration . Parameters within the shared-network but outside the enclosed subnet declarations are considered global parameters. The name of the shared-network should be a descriptive title for the network such as test-lab to describe all the subnets in a test lab environment. shared-network name { option domain-name "school.aiu.com"; option domain-name-servers ns1.aiu.com, ns2.redhat.com; option routers 192.168.1.254; more parameters for aiu shared-network subnet 192.168.1.0 netmask 255.255.255.0 { parameters for subnet range 192.168.1.1 192.168.1.31; } subnet 192.168.1.32 netmask 255.255.255.0 { parameters for subnet range 192.168.1.33 192.168.1.63; } } Shared-network Declaration The group declaration can be used to apply global parameters to a group of declarations. You can group shared networks, subnets, hosts, or other groups. Group Declaration To configure a DHCP server that leases a dynamic IP address to a system within a subnet, modify the diagram with your values. It declares a default lease time, maximum lease time, and network configuration values for the clients. This example assigns IP addresses in the range 192.168.1.10 and 192.168.1.100 to client systems. default-lease-time 600; max-lease-time 7200; option subnet-mask 255.255.255.0; option broadcast-address 192.168.1.255; option routers 192.168.1.254; option domain-name-servers 192.168.1.1, 192.168.1.2; option domain-name "example.com"; subnet 192.168.1.0 netmask 255.255.255.0 { range 192.168.1.10 192.168.1.100; } Range Parameter To assign an IP address to a client based on the MAC address of the network interface card, use the hardware ethernet parameter within a host declaration. As shown below the host apex declaration specifies that the network interface card with the MAC address 00:A0:78:8E:9E:AA always receives the IP address 192.168.1.4. Notice that you can also use the optional parameter host-name to assign a host name to the client.
Approximate Word count = 4378
Approximate Pages = 17.5
(250 words per page double spaced)
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