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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 22 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
slots, 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.
shows 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
corresponds 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 22-2
Suboption Packet Formats
shows the packet formats for user-configured remote-ID and circuit-ID suboptions The
switch uses these packet formats when DHCP snooping 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 from 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 byte
1 byte
116300
4
0
6
1
6
0
8
2
Module Port
1 byte 1 byte
2 bytes
VLAN
Содержание Catalyst 3750-E Series
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Страница 52: ...lii Catalyst 3750 E and 3560 E Switch Software Configuration Guide OL 9775 08 Preface ...
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