Cisco Ios Dhcp Server Database; Dhcp Snooping Binding Database - Cisco Catalyst 3120 Software Manual

Understanding DHCP Features
The values for these fields in the packets change from the default values when you configure the
remote-ID and circuit-ID suboptions:
•
•
Figure 21-3
Circuit ID Suboption Frame Format (for user-configured string):
Suboption
type
1 byte
Remote ID Suboption Frame Format (for user-configured string):
Suboption
type
1 byte

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.

DHCP Snooping Binding Database

When DHCP snooping is enabled, the switch uses the DHCP snooping binding database to store
information about untrusted interfaces. The database can have up to 8192 bindings.
Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
21-6
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.
–
User-Configured Suboption Packet Formats
Circuit
ID type
Length Length
1 N+2 1 N ASCII Circuit ID string
1 byte 1 byte 1 byte
Remote
ID type
Length Length
2 N+2 1 N
ASCII Remote ID string or hostname
1 byte 1 byte 1 byte
Chapter 21
N bytes (N = 3-63)
N bytes (N = 1-63)
Configuring DHCP Features and IP Source Guard
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