22-6
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 22 Configuring DHCP Features and IP Source Guard
Understanding DHCP Features
Figure 22-3
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.
Figure 22-3
User-Configured Suboption Packet Formats
Cisco IOS DHCP Server Database
During the DHCP-based autoconfiguration process, the designated DHCP server uses the Cisco IOS
DHCP server database. It has IP addresses,
address bindings
, and configuration parameters, such as the
boot file.
An address binding is a mapping between an IP address and a MAC address of a host in the Cisco IOS
DHCP server database. You can manually assign the client IP address, or the DHCP server can allocate
an IP address from a DHCP address pool. For more information about manual and automatic address
bindings, see the “Configuring DHCP” chapter of the
Cisco IOS IP Configuration Guide,
Release 12.2
.
Length
Length
Circuit
ID type
Suboption
type
Circuit ID Suboption Frame Format (for user-configured string):
Remote ID Suboption Frame Format (for user-configured string):
Suboption
type
Length
Length
Remote
ID type
145774
N
1
N+2
1
N
1
N+2
2
ASCII Circuit ID string
1 byte 1 byte 1 byte
N bytes (
N = 3-63)
ASCII Remote ID string or hostname
N bytes (
N = 1-63)
1 byte
1 byte 1 byte 1 byte
1 byte
Содержание 3750G - Catalyst Integrated Wireless LAN Controller
Страница 80: ...1 28 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 1 Overview Where to Go Next ...
Страница 606: ...27 8 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 27 Configuring UDLD Displaying UDLD Status ...
Страница 670: ...31 18 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 31 Configuring SNMP Displaying SNMP Status ...
Страница 1048: ...41 20 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 41 Configuring MSDP Monitoring and Maintaining MSDP ...
Страница 1086: ...43 26 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Chapter 43 Troubleshooting Using the crashinfo Files ...
Страница 1104: ...B 4 Catalyst 3750 Switch Software Configuration Guide OL 8550 02 Appendix B Supported MIBs Using FTP to Access the MIB Files ...