Cisco IOS DHCP Server

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Cisco IOS DHCP Server

• Configuring Cisco 2650
• Router
• By John Teissonniere
• Manny Jacome

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What Is Dynamic Host Control Protocol?

• Provides configuration parameters, such as
• Client IP address and subnet mask
• Default gateway

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Network Implementation

• Single LAN
• VLANs using a relay agent

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DHCP IOS Server
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How Does It Work

• DHCPDISCOVER (broadcast)
• UDP protocol, port 67
• Destination address of 255.255.255.255
• Source address 0.0.0.0
• Relay agent (ip helper-address)

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How Does It Work

• DHCPOFFER (unicast message can be from one or
  several DHCP servers)
• Offer on port 68
• Lease time
• Renewal time
• Domain name server
• Wins server
• DNS server

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How Does It Work

• DHCPREQUEST Broadcast (to all DHCP servers
  available)
• Server identifier option field
• No ip address yet

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How Does It Work

• DHCPACK(unicast)
• Contains network information
• Client in bound state

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Benefits of DHCP

• Reduced internet access costs
• Reduced client configuration tasks and costs
• Centralized management

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Configuring the Server

• Identify TFTP,FTP,RCP servers to store database
• Identify assignable IP addresses
• Identify DHCP options for devices
• Default router(s)
• DNS server(s)
• NetBIOS name server

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IPCONFIG / All
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To Configure Cisco IOS DHCP Server Feature
(Steps)

• Configure a DHCP database agent or
• disabling DHCP conflict login
• Excluded IP addresses
• Configure a DHCP address pool
• DHCP relay agent using IP helper-address command
  (performed at the switch)