Cisco IOS Software Configuration Guide for Cisco Aironet Access Points 12.3(7)JA
Configuring Multiple SSIDs
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Configuring Multiple SSIDs

Table Of Contents

Configuring Multiple SSIDs

Understanding Multiple SSIDs

Effect of Software Versions on SSIDs

Configuring Multiple SSIDs

Creating an SSID Globally

Viewing SSIDs Configured Globally

Using Spaces in SSIDs

Using a RADIUS Server to Restrict SSIDs

Configuring Multiple Basic SSIDs

Requirements for Configuring Multiple BSSIDs

Guidelines for Using Multiple BSSIDs

Configuring Multiple BSSIDs

CLI Configuration Example

Displaying Configured BSSIDs


Configuring Multiple SSIDs


This chapter describes how to configure and manage multiple service set identifiers (SSIDs) on the access point. This chapter contains these sections:

Understanding Multiple SSIDs

Configuring Multiple SSIDs

Configuring Multiple Basic SSIDs

Understanding Multiple SSIDs

The SSID is a unique identifier that wireless networking devices use to establish and maintain wireless connectivity. Multiple access points on a network or sub-network can use the same SSIDs. SSIDs are case sensitive and can contain up to 32 alphanumeric characters. Do not include spaces in your SSIDs.

You can configure up to 16 SSIDs on your access point and assign different configuration settings to each SSID. All the SSIDs are active at the same time; that is, client devices can associate to the access point using any of the SSIDs. These are the settings you can assign to each SSID:

VLAN

Client authentication method

Maximum number of client associations using the SSID

RADIUS accounting for traffic using the SSID

Guest mode

If you want the access point to allow associations from client devices that do not specify an SSID in their configurations, you can set up a guest SSID. The access point includes the guest SSID in its beacon.

If your network uses VLANs, you can assign one SSID to a VLAN, and client devices using the SSID are grouped in that VLAN.

Effect of Software Versions on SSIDs

Cisco introduced global-mode SSID configuration in Cisco IOS Release 12.3(2)JA to simplify configuration of SSID parameters under multiple interfaces. Configuration of SSID parameters at the interface level was supported in Cisco IOS Release 12.3(2)JA release for backward compatibility, but configuration of SSID parameters at the interface level will be totally disabled in releases after Cisco IOS Release 12.3(4)JA. Table 7-1 lists the SSID configuration methods supported in Cisco IOS Releases.

Table 7-1 SSID Configuration Methods Supported in Cisco IOS Releases 

Cisco IOS Release
Supported SSID Configuration Method

12.2(15)JA

Interface-level only

12.3(2)JA

Both interface-level and global

12.3(4)JA and 12.3(7)JA

Both interface-level and global; all SSIDs saved in global mode

post-12.3(4)JA

Global only


Cisco IOS Release 12.3(7)JA supports configuration of SSID parameters at the interface level on the CLI, but the SSIDs are stored in global mode. Storing all SSIDs in global mode ensures that the SSID configuration remains correct when you upgrade to release later than Cisco IOS Release 12.3(7)JA.

If you need to upgrade from Cisco IOS Release 12.3(2)JA or earlier to a release later than 12.3(4)JA, you should first upgrade to Cisco IOS Release 12.3(4)JA, save the configuration file, upgrade to the target release, and load the saved configuration file. This process ensures that your interface-level SSID configuration correctly translates to global mode. If you upgrade directly from a pre-12.3(4)JA release to a post-12.3(4)JA release, your interface-level SSID configuration is deleted.

If you downgrade the software version from Cisco IOS Release 12.3(7)JA, any SSIDs that you created become invalid. To avoid reconfiguring the SSIDs after a downgrade, save a copy of a configuration file in an earlier software version before you upgrade to Cisco IOS Release 12.3(7)JA; if you downgrade software versions from Cisco IOS Release 12.3(7)JA, load the saved configuration file after the downgrade.

Table 7-2 shows an example SSID configuration on an access point running Cisco IOS Release 12.2(15)JA and the configuration as it appears after upgrading to Cisco IOS Release 12.3(7)JA.

Table 7-2 Example: SSID Configuration Converted to Global Mode after Upgrade

SSID Configuration in 12.2(15)JA
SSID Configuration after Upgrade to 12.3(7)JA

interface dot11Radio 0

ssid engineering

authentication open

vlan 4

interface dot11Radio 1

ssid engineering

authentication open

vlan 5

dot11 ssid engineering

authentication open

vlan 5

!

interface dot11Radio 0

ssid engineering

interface dot11Radio 1

ssid engineering


Note that the VLAN configuration under each interface is retained in the global SSID configuration.


Note SSIDs, VLANs, and encryption schemes are mapped together on a one-to-one-to-one basis; one SSID can be mapped to one VLAN, and one VLAN can be mapped to one encryption scheme. When using a global SSID configuration, you cannot configure one SSID with two different encryption schemes. For example, you cannot apply SSID north with TKIP on interface dot11 0 and also apply SSID north with WEP128 on interface dot11 1.


Configuring Multiple SSIDs

These sections contain configuration information for multiple SSIDs:

Creating an SSID Globally

Using a RADIUS Server to Restrict SSIDs


Note In Cisco IOS Release 12.3(4)JA and later, you configure SSIDs globally and then apply them to a specific radio interface. Follow the instructions in the "Creating an SSID Globally" section to configure SSIDs globally.


Creating an SSID Globally

In Cisco IOS Releases 12.3(2)JA and later, you can configure SSIDs globally or for a specific radio interface. When you use the dot11 ssid global configuration command to create an SSID, you can use the ssid configuration interface command to assign the SSID to a specific interface.

When an SSID has been created in global configuration mode, the ssid configuration interface command attaches the SSID to the interface but does not enter ssid configuration mode. However, if the SSID has not been created in global configuration mode, the ssid command puts the CLI into SSID configuration mode for the new SSID.


Note SSIDs created in Cisco IOS Releases 12.3(7)JA and later become invalid if you downgrade the software version to an earlier release.


Beginning in privileged EXEC mode, follow these steps to create an SSID globally. After you create an SSID, you can assign it to specific radio interfaces.

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

dot11 ssid ssid-string

Create an SSID and enter SSID configuration mode for the new SSID. The SSID can consist of up to 32 alphanumeric characters. SSIDs are case sensitive.

Note +. ], ?, $, TAB, and trailing spaces are invalid characters for SSIDs.

Step 3 

authentication client
username
username
password password

(Optional) Set an authentication username and password that the access point uses to authenticate to the network when in repeater mode. Set the username and password on the SSID that the repeater access point uses to associate to a root access point, or with another repeater.

Step 4 

accounting list-name

(Optional) Enable RADIUS accounting for this SSID. For list-name, specify the accounting method list. Click this link for more information on method lists: http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fsecur_c/fsaaa/scfacct.htm#xtocid2

Step 5 

vlan vlan-id

(Optional) Assign the SSID to a VLAN on your network. Client devices that associate using the SSID are grouped into this VLAN. You can assign only one SSID to a VLAN.

Step 6 

guest-mode

(Optional) Designate the SSID as your access point guest-mode SSID. The access point includes the SSID in its beacon and allows associations from client devices that do not specify an SSID.

Step 7 

infrastructure-ssid [optional]

(Optional) Designate the SSID as the SSID that other access points and workgroup bridges use to associate to this access point. If you do not designate an SSID as the infrastructure SSID, infrastructure devices can associate to the access point using any SSID. If you designate an SSID as the infrastructure SSID, infrastructure devices must associate to the access point using that SSID unless you also enter the optional keyword.

Step 8 

interface dot11radio { 0 | 1 }

Enter interface configuration mode for the radio interface to which you want to assign the SSID. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.

Step 9 

ssid ssid-string

Assign the global SSID that you created in Step 2 to the radio interface.

Step 10 

end

Return to privileged EXEC mode.

Step 11 

copy running-config startup-config

(Optional) Save your entries in the configuration file.


Note You use the ssid command authentication options to configure an authentication type for each SSID.


Use the no form of the command to disable the SSID or to disable SSID features.

This example shows how to:

Name an SSID

Configure the SSID for RADIUS accounting

Set the maximum number of client devices that can associate using this SSID to 15

Assign the SSID to a VLAN

Assign the SSID to a radio interface

AP# configure terminal
AP(config)# dot11 ssid batman
AP(config-ssid)# accounting accounting-method-list
AP(config-ssid)# max-associations 15
AP(config-ssid)# vlan 3762
AP(config-ssid)# exit
AP(config)# interface dot11radio 0
AP(config-if)# ssid batman
 
   

Viewing SSIDs Configured Globally

Use this command to view configuration details for SSIDs that are configured globally:

AP# show running-config ssid ssid-string
 
   

Using Spaces in SSIDs

In Cisco IOS Release 12.3(7)JA, You can include spaces in an SSID, but trailing spaces (spaces at the end of an SSID) are invalid. However, any SSIDs created in previous versions having trailing spaces are recognized. Trailing spaces make it appear that you have identical SSIDs configured on the same access point. If you think identical SSIDs are on the access point, use the show dot11 associations privileged EXEC command to check any SSIDs created in a previous release for trailing spaces.

For example, this sample output from a show configuration privileged EXEC command does not show spaces in SSIDs:

ssid buffalo
    vlan 77
    authentication open
 
   
ssid buffalo
    vlan 17
    authentication open
 
   
ssid buffalo
    vlan 7
    authentication open
 
   

However, this sample output from a show dot11 associations privileged EXEC command shows the spaces in the SSIDs:

SSID [buffalo] :
SSID [buffalo ] :
SSID [buffalo  ] :
 
   

Using a RADIUS Server to Restrict SSIDs

To prevent client devices from associating to the access point using an unauthorized SSID, you can create a list of authorized SSIDs that clients must use on your RADIUS authentication server.

The SSID authorization process consists of these steps:

1. A client device associates to the access point using any SSID configured on the access point.

2. The client begins RADIUS authentication.

3. The RADIUS server returns a list of SSIDs that the client is allowed to use. The access point checks the list for a match of the SSID used by the client. There are three possible outcomes:

a. If the SSID that the client used to associate to the access point matches an entry in the allowed list returned by the RADIUS server, the client is allowed network access after completing all authentication requirements.

b. If the access point does not find a match for the client in the allowed list of SSIDs, the access point disassociates the client.

c. If the RADIUS server does not return any SSIDs (no list) for the client, then the administrator has not configured the list, and the client is allowed to associate and attempt to authenticate.

The allowed list of SSIDs from the RADIUS server are in the form of Cisco VSAs. The Internet Engineering Task Force (IETF) draft standard specifies a method for communicating vendor-specific information between the access point and the RADIUS server by using the vendor-specific attribute (attribute 26). Vendor-specific attributes (VSAs) allow vendors to support their own extended attributes not suitable for general use. The Cisco RADIUS implementation supports one vendor-specific option by using the format recommended in the specification. Cisco vendor-ID is 9, and the supported option has vendor-type 1, which is named cisco-avpair. The Radius server is allowed to have zero or more SSID VSAs per client.

In this example, the following AV pair adds the SSID batman to the list of allowed SSIDs for a user:

cisco-avpair= "ssid=batman"
 
   

For instructions on configuring the access point to recognize and use VSAs, see the "Configuring the Access Point to Use Vendor-Specific RADIUS Attributes" section.

Configuring Multiple Basic SSIDs

Access point 802.11a and 802.11g radios now support up to 8 basic SSIDs (BSSIDs), which are similar to MAC addresses. You use multiple BSSIDs to assign a unique DTIM setting for each SSID and to broadcast more than one SSID in beacons. A large DTIM value increases battery life for power-save client devices that use an SSID, and broadcasting multiple SSIDs makes your wireless LAN more accessible to guests.


Note Devices on your wireless LAN that are configured to associate to a specific access point based on the access point MAC address (for example, client devices, repeaters, hot standby units, or workgroup bridges) might lose their association when you add or delete a multiple BSSID. When you add or delete a multiple BSSID, check the association status of devices configured to associate to a specific access point. If necessary, reconfigure the disassociated device to use the BSSID's new MAC address.


Requirements for Configuring Multiple BSSIDs

To configure multiple BSSIDs, your access points must meet these minimum requirements:

VLANs must be configured

Access points must run Cisco IOS Release 12.3(4)JA or later

Access points must contain an 802.11a or 802.11g radio that supports multiple BSSIDs. To determine whether a radio supports multiple basic SSIDs, enter the show controllers radio_interface command. The radio supports multiple basic SSIDs if the results include this line:

Number of supported simultaneous BSSID on radio_interface: 8 
 
   

Guidelines for Using Multiple BSSIDs

Keep these guidelines in mind when configuring multiple BSSIDs:

RADIUS-assigned VLANs are not supported when you enable multiple BSSIDs.

When you enable BSSIDs, the access point automatically maps a BSSID to each SSID. You cannot manually map a BSSID to a specific SSID.

When multiple BSSIDs are enabled on the access point, the SSIDL IE does not contain a list of SSIDs; it contains only extended capabilities.

Any Wi-Fi certified client device can associate to an access point using multiple BSSIDs.

You can enable multiple BSSIDs on access points that participate in WDS.

Configuring Multiple BSSIDs

Follow these steps to configure multiple BSSIDs:


Step 1 Browse to the Global SSID Manager page on the access point GUI. (If you use the CLI instead of the GUI, refer to the CLI commands listed in the CLI Configuration Example at the end of this section.) Figure 7-1 shows the top portion of the Global SSID Manager page.

Figure 7-1 Global SSID Manager Page

Step 2 Enter the SSID name in the SSID field.

Step 3 Use the VLAN drop-down menu to select the VLAN to which the SSID is assigned.

Step 4 Select the radio interfaces on which the SSID is enabled. The SSID remains inactive until you enable it for a radio interface.

Step 5 Enter a Network ID for the SSID in the Network ID field.

Step 6 Assign authentication, authenticated key management, and accounting settings to the SSID in the Authentication Settings, Authenticated Key Management, and Accounting Settings sections of the page. BSSIDs support all the authentication types that are supported on SSIDs.

Step 7 (Optional) In the Multiple BSSID Beacon Settings section, select the Set SSID as Guest Mode check box to include the SSID in beacons.

Step 8 (Optional) To increase the battery life for power-save clients that use this SSID, select the Set Data Beacon Rate (DTIM) check box and enter a beacon rate for the SSID. The beacon rate determines how often the access point sends a beacon containing a Delivery Traffic Indicator Message (DTIM).

When client devices receive a beacon that contains a DTIM, they normally wake up to check for pending packets. Longer intervals between DTIMs let clients sleep longer and preserve power. Conversely, shorter DTIM periods reduce the delay in receiving packets but use more battery power because clients wake up more often.

The default beacon rate is 2, which means that every other beacon contains a DTIM. Enter a beacon rate between 1 and 100.


Note Increasing the DTIM period count delays the delivery of multicast packets. Because multicast packets are buffered, large DTIM period counts can cause a buffer overflow.


Step 9 In the Guest Mode/Infrastructure SSID Settings section, select Multiple BSSID.

Step 10 Click Apply.


CLI Configuration Example

This example shows the CLI commands that you use to enable multiple BSSIDs on a radio interface, create an SSID called visitor, designate the SSID as a BSSID, specify that the BSSID is included in beacons, set a DTIM period for the BSSID, and assign the SSID visitor to the radio interface:

ap(config)# interface d0
ap(config-if)# mbssid
ap(config-if)# exit
ap(config)# dot11 ssid visitor
ap(config-ssid)# mbssid guest-mode dtim-period 75
ap(config-ssid)# exit
ap(config)# interface d0
ap(config-if)# ssid visitor
 
   

You can also use the dot11 mbssid global configuration command to simultaneously enable multiple BSSIDs on all radio interfaces that support multiple BSSIDs.

Displaying Configured BSSIDs

Use the show dot11 bssid privileged EXEC command to display the relationship between SSIDs and BSSIDs or MAC addresses. This example shows the command output:

AP1230#show dot11 bssid
Interface     BSSID           Guest  SSID
Dot11Radio1   0011.2161.b7c0  Yes  atlantic
Dot11Radio0   0005.9a3e.7c0f  Yes  WPA2-TLS-g
 
   


Note When multiple BSSIDs are enabled on the access point, the SSIDL IE does not contain a list of SSIDs; it contains only extended capabilities.