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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter21 Configuring DHCP Feat ures and IP Source Guard Understanding DHCP Features
Remote-ID suboption fields
Suboption type
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 switch with
Cisco dual SFP X2 converter modules in the 10-Gigabit Ethernet module slots, port 1 is the internal
Gigabit Ethernet 1/0/1 port, port 2 is the internal Gigabit Eth ernet1/0/2 port, and so on. For the external
uplink ports (port 17 to port 20), port 17 is the Gigabit Eth erne t 1/ 0 /17 p ort, p ort 18 is the Gi gabi t
Ethernet 1/0/18 port, and so on. Because ports 21, 22, 23, and 24 are small form-factor pluggable (SFP)
modules, port 21 is the Gigabit Ethernet1/0/21 port, port 22 is the Gigab it Ethernet1/0/22 port, and so on.
Figure 21-2 shows the packet formats for the remote-ID suboption and the circuit-ID suboption when
the default suboption configuration is used. For the circuit-ID s ubop tio n, the modu le num be r
corresponds to the switch number in the stack. The swit ch us es t he pa cket fo rmat s when y ou globa lly
enable DHCP snooping and enter the ip dhcp snooping information option global configuration
command.
Figure21-2 Suboption Packet Formats
Figure 21-3 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.
Length Length
Circuit
ID type
S
uboption
type
C
ircuit ID Suboption Frame Format
R
emote ID Suboption Frame Format
6 bytes
MAC address
1 byte 1 byte 1 byte
S
uboption
type
1 byte
Length Length
Remote
ID type
1 byte 1 byte 1 byte1 byte
1
16300
4061
6082
Module Port
1 byte 1 byte2 bytes
VLAN