Cisco Catalyst 3560-X Series, Руководство по настройке программного обеспечения

Страница: 657 / 1538

1-5
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 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.
Figure 1-2 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 1-2 Suboption Packet Formats
Figure 1-3 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