Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide, Rel. 12.2(25)SEF1

17-5
Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
OL-8915-01
Chapter 17 Configuring DHCP Features
Understanding DHCP Features
– Length of the suboption type
– Remote-ID type
– Length of the remote-ID type
In the port field of the circuit ID suboption, the port numbers start at 1. For example, on a Cisco Catalyst
Blade Switch 3020 for HP, which has 24 ports, port 1 is the Gigabit Ethernet 0/1 port, port 2 is the
Gigabit Ethernet 0/2 port, port 3 is the Gigabit Ethernet 0/3 port, and so on. Ports 17 to 20 are
dual-purpose SFP module/RJ-45 copper Ethernet uplink ports Gi0/17 to Gi0/20. Ports 21x and 22x are
copper 10/100/1000BASE-T ports Gi0/21 and Gi0/22. Ports 23x and 24x are dual-purpose
external/internal 10/100/1000BASE-T copper uplink ports Gi0/23 and Gi0/24.
Figure 17-2 shows the packet formats for the remote-ID suboption and the circuit-ID suboption. The
switch uses the packet formats when you globally enable DHCP snooping and enter the ip dhcp
snooping information option global configuration command.
Figure 17-2 Suboption Packet Formats
Figure 17-2 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.
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