Cisco Catalyst 3750-X User Manual

24-5
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 24 Configuring DHCP Features and IP Source Guard
Understanding DHCP Features
In the port field of the circuit ID suboption, the port numbers start at 3. For example, on a
Catalyst 3750-E switch with 24 10/100/1000 ports and four small form-factor pluggable (SFP) module
slo
ts, port 3 is the Gigabit Ethernet 1/0/1 port, port 4 is the Gigabit Ethernet 1/0/2 port, and so forth.
Port 27 is the SFP module slot Gigabit
Ethernet1/0/25, and so forth.
Figure 24-2 s
hows the packet formats for the remote-ID suboption and the circuit-ID suboption when
the default suboption configuration is used. For the circuit-ID suboption, the module number
corre
sponds to the switch number in the stack. The switch uses the packet formats when you globally
enable DHCP snooping and enter the ip dhcp snooping information option global configuration
command.
Figure 24-2 Suboption Packet Formats
Figure 24-3 shows the packet formats for user-configured remote-ID and circuit-ID suboptions The
switch uses these packet formats when DHCP sno
oping is globally enabled and when the ip dhcp
snooping information option format remote-id global configuration command and the ip dhcp
snooping vlan information option format-type circuit-id string interface configuration command are
entered.
The values for these fields in the packets change fro
m the default values when you configure the
remote-ID and circuit-ID suboptions:
• Circuit-ID suboption fields
– The circuit-ID type is 1.
– The length values are variable, depending on the length of the string that you configure.
• Remote-ID suboption fields
– The remote-ID type is 1.
– The length values are variable, depending on the length of the string that you configure.
Length Length
Circuit
ID type
Suboption
type
Circuit ID Suboption Frame Format
Remote ID Suboption Frame Format
6 bytes
MAC address
1 byte 1 byte 1 byte
Suboption
type
1 byte
Length Length
Remote
ID type
1 byte 1 byte 1 byte1 byte
116300
4061
6082
Module Port
1 byte 1 byte2 bytes
VLAN

Cisco Catalyst 3750-X Specifications

General

Switching Capacity	160 Gbps
Stacking Bandwidth	64 Gbps
Max Stacking Units	9
Layer Support	Layer 2 and Layer 3
Form Factor	Rack-mountable
DRAM	256 MB
Flash Memory	64 MB
Model	Cisco Catalyst 3750-X Series
Ports	24 or 48 10/100/1000 Ethernet ports
Uplink Interfaces	4 SFP or 2 SFP+
Features	StackWise Plus, EnergyWise
Image	IP Base or IP Services
Operating Temperature	0 to 40°C
Operating Humidity	10 to 85% noncondensing