Cisco Catalyst 3750 User Manual

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Catalyst 3750 Switch Command Reference
OL-8552-07
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
ip dhcp snooping information option
ip dhcp snooping information option
Use the ip dhcp snooping information option global configuration command to enable DHCP
option-82 data insertion. Use the no form of this command to disable DHCP option-82 data insertion.
ip dhcp snooping information option
no ip dhcp snooping information option
Syntax Description This command has no arguments or keywords.
Defaults DHCP option-82 data is inserted.
Command Modes Global configuration
Command History
Usage Guidelines You must globally enable DHCP snooping by using the ip dhcp snooping global configuration
command for any DHCP snooping configuration to take effect.
When the option-82 feature is enabled and a switch receives a DHCP request from a host, it adds the
option-82 information in the packet. The option-82 information contains the switch MAC address (the
remote ID suboption) and the port identifier, vlan-mod-port, from which the packet is received (circuit
ID suboption). The switch forwards the DHCP request that includes the option-82 field to the DHCP
server.
When the DHCP server receives the packet, it can use the remote ID, the circuit ID, or both to assign IP
addresses and implement policies, such as restricting the number of IP addresses that can be assigned to
a single remote ID or a circuit ID. Then the DHCP server echoes the option-82 field in the DHCP reply.
The DHCP server unicasts the reply to the switch if the request was relayed to the server by the switch.
When the client and server are on the same subnet, the server broadcasts the reply. The switch inspects
the remote
ID and possibly the circuit ID fields to verify that it originally inserted the option-82 data.
The switch removes the option-82 field and forwards the packet to the switch port that connects to the
DHCP host that sent the DHCP request.
Examples This example shows how to enable DHCP option-82 data insertion:
Switch(config)# ip dhcp snooping information option
You can verify your settings by entering the show ip dhcp snooping user EXEC command.
Release Modification
12.1(19)EA1 This command was introduced.

Cisco Catalyst 3750 Specifications

General

Device Type	Switch
Switching Capacity	32 Gbps
Forwarding Rate	38.7 Mpps
Stacking Bandwidth	32 Gbps
RAM	128 MB
Jumbo Frame Support	Yes
Switch Type	Managed
Model	Catalyst 3750 Series
Uplink Interfaces	SFP
Form Factor	Rack-mountable
MAC Address Table Size	12, 000 entries
Routing Protocol	RIP, OSPF, EIGRP
Remote Management Protocol	SNMP, Telnet, HTTP
Features	Layer 3 switching, Layer 2 switching, auto-negotiation, BOOTP support, ARP support, VLAN support, auto-uplink (auto MDI/MDI-X), IGMP snooping, traffic shaping, MAC address filtering, Quality of Service (QoS), Jumbo Frames support, MLD snooping, Dynamic ARP Inspection (DAI), Cisco EnergyWise technology
Power over Ethernet (PoE)	PoE
Operating Temperature	-5 - 45 °C
Operating Humidity	10% to 85% non-condensing