Filter
Top Products
19-5
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 19 Configuring DHCP Features
Configuring DHCP Features
The port numbers in the port field of the circuit-ID suboption start at 0. For example, on a
Catalyst
2950G-24-EI switch, port 0 is the Fast Ethernet 0/1 port, port 1 is the Fast Ethernet 0/2 port,
port
2 is the Fast Ethernet 0/3 port, and so on. Port 24 is the Gigabit Interface Converter (GBIC)-based
Gigabit module slot 0/1, and port
25 is the GBIC-based Gigabit module slot 0/2.
Figure 19-2 shows the packet formats for the remote ID suboption and the circuit ID suboption. The
switch uses the packet formats when DHCP snooping is globally enabled and when the ip dhcp
snooping information option global configuration command is entered. For the circuit ID suboption,
the module field is always zero.
Figure 19-2 Suboption Packet Formats
Configuring DHCP Features
These sections describe how to configure DHCP snooping and option 82 on your switch:
• Default DHCP Configuration, page 19-5
• DHCP Snooping Configuration Guidelines, page 19-6
• Configuring the DHCP Server, page 19-7
• Enabling DHCP Snooping and Option 82, page 19-7
Default DHCP Configuration
Table 19-1 shows the default DHCP configuration.
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 byte1 byte
116300
4061
6082
Module Port
1 byte 1 byte2 bytes
VLAN