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amercer00
Contributor

"DFS Band 3 Block" default on Cisco AP's

What is the purpose of "dfs band 3 block"?

Do I want/need to block band 3 for indoor wireless networks?

Any advantages/disadvantages of unblocking it?

Thanks,

Allen

1 ACCEPTED SOLUTION

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Yes you are correct

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5 REPLIES 5
Prakash Parvathala
Enthusiast

Access points with 5-GHz radios configured at the factory for use in the United States, Europe, Singapore, Korea, Japan, Israel, and Taiwan now comply with regulations that require radio devices to use Dynamic Frequency Selection (DFS) to detect radar signals and avoid interfering with them. When an access points detects a radar on a certain channel, it avoids using that channel for 30 minutes. Radios configured for use in other regulatory domains do not use DFS.

When a DFS-enabled 5-GHz radio operates on one of the 15 channels, the access point automatically uses DFS to set the operating frequency. When DFS is enabled, the access point monitors its operating frequency for radar signals.

For more info about DFS and configurations, please read Radio Configuration settings

So why do Cisco AP's block "Band 3" by default?

Can I unblock it with "no dfs band block", or should I leave it blocked?

mohanak
Cisco Employee

If your regulatory domain limits the channels that you can use in specific locations--for example, indoors or outdoors--you can block groups of channels to prevent the access point from selecting them when DFS is enabled. Use this configuration interface command to block groups of channels from DFS selection:

[no] dfs band [1] [2] [3] [4] block

The 1, 2, 3, and 4 options designate blocks of channels:

1—Specifies frequencies 5.150 to 5.250 GHz. This group of frequencies is also known as the UNII-1 band.

2—Specifies frequencies 5.250 to 5.350 GHz. This group of frequencies is also known as the UNII-2 band.

3—Specifies frequencies 5.470 to 5.725 GHz.

4—Specifies frequencies 5.725 to 5.825 GHz. This group of frequencies is also known as the UNII-3 band.

This example shows how to prevent the access point from selecting frequencies 5.150 to 5.350 GHz during DFS:

ap(config-if)# dfs band 1 2 block

This example shows how to unblock frequencies 5.150 to 5.350 for DFS:

ap(config-if)# no dfs band 1 2 block

This example shows how to unblock all frequencies for DFS:

ap(config-if)# no dfs band block

So, in the USA, if the FCC says " UNII-3/ISM band is intended for outdoor bridge products and may be used for indoor WLANs as well", then I can unblock it and use ALL bands indoors, correct?

Yes you are correct

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