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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter21 Configuring DHCP Features and IP Source Guard
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:
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.
Figure21-3 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 ho st i n the Cisc o IO S
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 ab out m anua l a nd aut omat ic addr ess
bindings, see the “Configuring DHCP” chapter of the Cisco IOS IP Con figuration Guide,
Release 12.2.
DHCP Snooping Binding Database
When DHCP snooping is enabled, the switch uses the DHCP snoopi ng bind ing databa se to stor e
information about untrusted interfaces. The database can have up to 8192 bindings.
Length Length
Circuit
ID type
S
uboption
type

C

ircuit ID Suboption Frame Format (for user-configured string):

R

emote ID Suboption Frame Format (for user-configured string):

S
uboption
type Length Length
Remote
ID type
145774
N1N+2 1
N1N+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 byte1 byte