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Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-29225-01
Chapter 6 Configuring Radio Settings
Disabling and Enabling Short Radio Preambles
Use the no form of the command to disable world mode.
Disabling and Enabling Short Radio Preambles
The radio preamble (sometimes called a header) is a section of data at the head of a packet that contains
information that the wireless device and client devices need when sending and receiving packets. You
can set the radio preamble to long or short:
• Short—A short preamble improves throughput performance. Cisco Aironet Wireless LAN Client
Adapters support short preambles. Early models of Cisco Aironet's Wireless LAN Adapter (PC4800
and PC4800A) require long preambles.
• Long—A long preamble ensures compatibility between the wireless device and all early models of
Cisco Aironet Wireless LAN Adapters (PC4800 and PC4800A). If these client devices do not
associate to the wireless devices, you should use short preambles.
You cannot configure short or long radio preambles on the 5-GHz radio.
Beginning in privileged EXEC mode, follow these steps to disable short radio preambles:
Step 3
world-mode
dot11d country_code code
{ both | indoor | outdoor }
world-mode roaming
| legacy
Enable world mode.
• Enter the dot11d option to enable 802.11d world mode.
–
When you enter the dot11d option, you must enter a
two-character ISO country code (for example, the ISO
country code for the United States is US). You can find
a list of ISO country codes at the ISO website.
–
After the country code, you must enter indoor,
outdoor, or both to indicate the placement of the
wireless device.
• Enter the legacy option to enable Cisco legacy world
mode.
• Enter the world-mode roaming to place the access point
in a continuous world mode configuration.
Note Aironet extensions must be enabled for legacy world
mode operation, but Aironet extensions are not
required for 802.11d world mode. Aironet extensions
are enabled by default.
Step 4
end Return to privileged EXEC mode.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface dot11radio { 0 } Enter interface configuration mode for the 2.4-GHz radio
interface.
Step 3
no preamble-short Disable short preambles and enable long preambles.