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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Configuring DHCP Features and IP Source Guard
This chapter describes how to configure DHCP snooping and option-82 data insertion, and the DHCP
server port-based address allocation features on the Cisco ME 3400 Ethernet Access switch. It also
describes how to configure the IP source guard feature, which is supported on switches running the metro
access and metro IP access images.
Note For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release, and see the “DHCP Commands” section in the Cisco IOS IP Command
Reference, Volume 1 of 3: Addressing and Services, Release 12.2.
This chapter consists of these sections:
• Understanding DHCP Features, page 19-1
• Configuring DHCP Features, page 19-7
• Displaying DHCP Snooping Information, page 19-15
• Understanding IP Source Guard, page 19-15
• Configuring IP Source Guard, page 19-16
• Displaying IP Source Guard Information, page 19-19
• Understanding DHCP Server Port-Based Address Allocation, page 19-19
• Configuring DHCP Server Port-Based Address Allocation, page 19-19
• Displaying DHCP Server Port-Based Address Allocation, page 19-22

Understanding DHCP Features

DHCP is widely used in LAN environments to dynamically assign host IP addresses from a centralized
server, which significantly reduces the overhead of administration of IP addresses. DHCP also helps
conserve the limited IP address space because IP addresses no longer need to be permanently assigned
to hosts; only those hosts that are connected to the network consume IP addresses.
These sections contain this information:
• DHCP Server, page 19-2
• DHCP Relay Agent, page 19-2
• DHCP Snooping, page 19-2
• Option-82 Data Insertion, page 19-3