H3C Wireless Products FAQ(V7)-6W100

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H3C Wireless Products FAQ(V7)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Document version: 6W102-20190603

 

Copyright © 2019 New H3C Technologies Co., Ltd. All rights reserved.

No part of this manual may be reproduced or transmitted in any form or by any means without prior written consent of New H3C Technologies Co., Ltd.

Except for the trademarks of New H3C Technologies Co., Ltd., any trademarks that may be mentioned in this document are the property of their respective owners.

The information in this document is subject to change without notice.


Contents

Introduction· 1

Protocols and standards· 1

Q.     What is the most recent wireless networking standard?· 1

Q.     What are the frequency, compatibility, and maximum rate of 802.11a/b/g/n/ac?· 1

Q.     Is wireless networking protocol 802.11 a Layer 2 networking protocol?· 1

Q.     How many channels are available in the 2.4 GHz band in China? What is the bandwidth for each channel? Why only three channels are used in WLAN deployment?· 1

Q.     Which techniques does 802.11ac use to increase channel bandwidth and expand the signal coverage?· 1

Q.     What are the relationships among 802.11i, WPA, WPA2, PSK, 802.1X, TKIP, CCMP, and AES?· 2

Q.     What interference might exist in a WLAN and how seriously can they affect a WLAN?· 2

Q.     Does the rate of a WLAN represent the uplink rate or the downlink rate?· 2

Access points (APs) 2

Q.     What are the functions of fit APs?· 2

Q.     How can I view the serial ID of a fit AP? What are the functions of a serial ID?· 2

Q.     Do I need to configure ACs' IP addresses for a fit AP?· 2

Q.     Do fit APs support PoE power supply?· 3

Q.     How does a fit AP select a channel when starting up? Can the fit AP change its channel while operating?· 3

Q.     Does a fit AP have a console port? Can I log in from the console port to configure the AP?· 3

Q.     Under what circumstances can I return an AP for repair?· 3

Q.     Can a fit AP cooperate with a third-party AC?· 3

Q.     Can a radio bound to different SSIDs operate on different channels?· 3

Q.     Why is the transmit rate dynamically adjusted in a WLAN?· 3

Q.     How can I associate fit APs with an AC?· 3

Q.     Can a manual AP download a version from the AC and then connect to the AC if it has a different software version than the AC?· 4

Q.     Can an auto AP download a version from the AC and then connect to the AC if it has a different software version than the AC?· 4

Q.     Why can't I configure an auto AP?· 4

Q.     Do fit APs save configuration? How do I upgrade a large number of fit APs in batch?· 4

Q.     Can ACs provide services to wired users?· 4

Q.     How many AC IP addresses does a fit AP support in Option 43?· 4

Q.     Can an AP work in fat AP mode?· 4

Q.     How can I view the software version of a fit AP?· 4

Access controllers (ACs) 5

Q.     What are the functions of an AC?· 5

Q.     How can I connect a fit AP to an AC physically?· 5

Q.     How does an AC communicate with a fit AP?· 5

Q.     Can an AC act as a local DHCP server?· 5

Q.     How can I view detailed information about manual APs and online auto APs on an AC?· 5

Q.     How can I view the association status of APs on an AC?· 5

Q.     How can I view the version of an AC?· 5

Q.     How can I view channel information on an AC?· 5

Q.     How can I separate services of different APs with the same SSID?· 5

Q.     Can I log off a client?· 5

Q.     What's the difference between the online time and the system up time in the output from the display wlan ap name verbose command?· 6

Q.     How can I view information about APs that went offline recently on an AC?· 6

Q.     Which UDP ports does a CAPWAP tunnel use?· 6

Q.     Why can't I view newly created manual APs in the system-defined AP group?· 6

Q.     Does an AC support backup?· 6

Q.     Do ACs support IRF? How many ACs does an IRF fabric support?· 6

Q.     How can I configure clients to automatically access another WLAN when the uplink of the associated AC is down?· 7

Q.     Do ACs support third-party APs?· 7

Q.     What are the advantages of local forwarding? When do I need to configure local forwarding?· 7

Licenses· 7

Q.     How do I increase the number of APs that an AC can manage?· 7

Q.     How do I know which features require licenses?· 7

Q.     How can I register and activate a license?· 7

Q.     How can I view the remaining days of AP licenses?· 7

Q.     How can I view the number of AP licenses?· 7

Q.     Do I need to restart the device for the license to take effect after installing a license?· 8

Q.     Will the installed licenses be deleted when the file system is formatted?· 8

Q.     Can I edit a license file?· 8

Q.     In an IRF fabric, how does the use of licenses change after a member AC leaves the fabric?· 8

Networking· 8

Q.     How is an AP associated with an AC in different fit AP+AC networking environments?· 8

Q.     At which layer can I deploy an AC in a fit AP+AC network?· 9

Q.     Do I need to change the wired backbone network for WLAN devices?· 9

Q.     How are packets forwarded by default in a fit AP+AC network?· 9

WLAN security· 9

Q.     Which authentication methods does an AC support?· 9

Q.     Can I configure local forwarding and centralized authentication at the same time when portal authentication is used?· 9

Q.     Does an AC support portal authentication?· 9

Q.     Can an AC cooperate with a third-party LDAP server for authentication?· 9

Q.     In a wireless network, which device acts as an AAA authenticator?· 9

Q.     Can an AC detect rogue APs?· 9

WLAN roaming· 10

Q.     What is WLAN roaming? How many types of WLAN roaming are available?· 10

Q.     Can wireless clients perform Layer 3 roaming?· 10

Q.     Do clients need to be reauthenticated or log in again after roaming?· 10

Q.     During WLAN roaming, will a client keep its subnet attributes such as the assigned VLAN, ACL, and routing policies?· 10

Q.     Does the IP address of a client remain unchanged during WLAN roaming?· 10

Q.     How can I adjust the sensitivity of a wireless NIC?· 10

Q.     Do I need to change the switch or router configuration to enable WLAN roaming?· 10

Q.     Do I need to install new client software for WLAN roaming?· 10

System management 10

Q.     Can I configure a mandatory rate for an AC to increase the wireless network performance?· 10

Q.     How can I determine whether memory leakage has occurred?· 11

Q.     How can I view process state information?· 11

Q.     How can I view memory usage for all processes?· 11

IRF· 11

Q.     Is there an upper limit on the number of member devices of an IRF fabric?· 11

Q.     Does an IRF fabric have requirements on the software versions of its member devices?· 11

Q.     Are there any requirements on IRF bridge MAC addresses when two IRF fabrics merge?· 11

Q.     Do I need to disable STP on switch interfaces when member devices are connected through a Layer 2 network?· 11

Q.     Under what circumstances do I need to use a switching device to form a star-topology IRF fabric?· 11

Q.     What restrictions and guidelines do I need to follow after an IRF fabric is formed?· 12


Wireless products FAQ

Introduction

This document contains the most frequently asked questions about wireless products.

Protocols and standards

This section contains the most frequently asked questions about wireless networking standards and protocols.

Q.     What is the most recent wireless networking standard?

A.     802.11 is a set of specifications created and maintained by the Institute of Electrical and Electronics Engineers (IEEE) for WLAN communication. The 802.11 family includes 802.11, 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac. The most recent wireless networking standard is 802.11ac.

Q.     What are the frequency, compatibility, and maximum rate of 802.11a/b/g/n/ac?

A.     The following table describes the frequency, compatibility, and maximum rate of 802.11a/b/g/n/ac:

Protocols

Frequency

Compatibility

Maximum rate

802.11a

5 GHz

N/A

54 Mbps

802.11b

2.4 GHz

N/A

11 Mbps

802.11g

2.4 GHz

Compatible with 802.11b

54 Mbps

802.11n

2.4 GHz, 5 GHz

Compatible with 802.11a/b/g

600 Mbps

802.11ac

5 GHz

Compatible with 802.11a/b/g/n

1.3 Gbps

 

Q.     Is wireless networking protocol 802.11 a Layer 2 networking protocol?

A.     Yes. 802.11 defines only contents of the PHY layer and the MAC layer of the data link layer in the OSI model. Other layers of a wireless network are the same as those of a wired network.

Q.     How many channels are available in the 2.4 GHz band in China? What is the bandwidth for each channel? Why only three channels are used in WLAN deployment?

A.     13 channels are available in the 2.4 GHz band in China. Each channel has a bandwidth of 22 MHz. To avoid interference caused by overlapping channels, only the three non-overlapping channels (typically channels 1, 6, and 11) in the 2.4 GHz band can be used in WLAN deployment.

Q.     Which techniques does 802.11ac use to increase channel bandwidth and expand the signal coverage?

A.     802.11ac uses the following techniques:

·     Uses increased spatial streams and high-density modulation.

·     Uses Multi-User Multiple-Input Multiple-Output (MU-MIMO) to increase data rates.

·     Improves channel utilization by using A-MPDU.

Q.     What are the relationships among 802.11i, WPA, WPA2, PSK, 802.1X, TKIP, CCMP, and AES?

A.     The 802.11i standard specifies security mechanisms for wireless networks.

·     WPA and WPA2 are two standards developed by the WiFi Alliance based on the draft of 802.11i before 802.11i was released.

·     PSK and 802.1X are two authentication methods for wireless networks. PSK is simple and is intended for personal use. 802.1X is complex, more secure, and is intended for enterprise use.

·     TKIP and CCMP are two encryption algorithms. AES is the core algorithm of CCMP and also the most secure encryption algorithm.

Q.     What interference might exist in a WLAN and how seriously can they affect a WLAN?

A.     WLAN devices operate in the 2.4 GHz industrial, scientific and medical (ISM) band or 5 GHz band.

2.4 GHz ISM band is reserved for the use in industrial, scientific and medical fields other than telecommunications. Devices that can use the 2.4 GHz band include microwave ovens, cordless phones, and Bluetooth devices. Interference severity of cordless phones, microwave ovens (within 3 meters), and Bluetooth devices such as laptop and PDA are in descending order.

Compared with the 2.4 GHz band, the 5 GHz band has less interference. Interference in the 5 GHz band includes radar, wireless sensors, digital satellites, wireless ATMs, and software-defined radios.

Q.     Does the rate of a WLAN represent the uplink rate or the downlink rate?

A.     WLANs work in half duplex mode and cannot receive and send packets at the same time. The rate of a WLAN typically refers to the sum of the uplink and downlink rates.

Access points (APs)

This section contains the most frequently asked questions about APs.

Q.     What are the functions of fit APs?

A.     A fit AP provides the following functions:

·     Provides communications from wireless clients to a wired network.

·     Transfers packet formats between 802.3 and 802.11.

·     Encrypts data frames and control frames through WEP, TKIP, or CCMP.

·     Buffers data and forwards packets based on QoS configuration.

·     Scans working channels to locate wireless clients and detect rogue APs and ad hoc clients.

·     Automatically obtains configurations from the associated AC.

Q.     How can I view the serial ID of a fit AP? What are the functions of a serial ID?

A.     You can view the serial ID of an AP on the rear panel of the AP, or you can display AP information on the AC to view an AP's serial ID.

A serial ID uniquely identifies an AP and must be specified when you create an AP on an AC.

Q.     Do I need to configure ACs' IP addresses for a fit AP?

A.     You can configure ACs' IP addresses for a fit AP, or the fit AP can obtain ACs' IP addresses automatically.

Q.     Do fit APs support PoE power supply?

A.     Fit APs that have PoE ports support PoE power supply. For APs with high power consumption, PoE+ power sourcing equipment conforming to 802.3at protocol is required.

Q.     How does a fit AP select a channel when starting up? Can the fit AP change its channel while operating?

A.     By default, a fit AP automatically selects a channel when starting up. The selected channel does not change when the AP is operating unless radar signals are detected on the working channel or DFS is configured.

Q.     Does a fit AP have a console port? Can I log in from the console port to configure the AP?

A.     Yes. By default, fit APs do not have any configuration and do not need to be configured. For management purposes, you can log in and configure the AP before it is associated with an AC. To configure a fit AP from the console after it is associated with an AC, you must enable  the AP automatically disables the login function unless the function is enabled for the AP on the AC.

Q.     Under what circumstances can I return an AP for repair?

A.     You can return an AP for repair if any of the following events occur:

·     The AP cannot start up, even if from the BootWare menu.

·     An error message occurs when the AP starts up, and you cannot press Ctrl+B to enter the Boot menu to upgrade the AP.

·     The Ethernet port on the AP cannot communicate with the switch even if you replace the cable or connect the Ethernet port to another port on the switch.

·     The output from the display current-configuration command shows that no radio exists on the AP after the AP starts up.

Q.     Can a fit AP cooperate with a third-party AC?

A.     No.

Q.     Can a radio bound to different SSIDs operate on different channels?

A.     No. A radio can operate only on one channel.

Q.     Why is the transmit rate dynamically adjusted in a WLAN?

A.     When wireless signal strength gets worse, the transmit rate will be reduced to decrease the error code ratio.

Q.     How can I associate fit APs with an AC?

A.     You can create manual APs or enable auto AP on the AC.

If auto AP is disabled, only APs with manual AP configuration can be associated with the AC.

If auto AP is enabled, APs can be associated with the AC without manual AP configuration. The AC names auto APs by their MAC addresses. This feature simplifies configuration when you deploy a large number of APs in a WLAN.

Q.     Can a manual AP download a version from the AC and then connect to the AC if it has a different software version than the AC?

A.     Yes.

Q.     Can an auto AP download a version from the AC and then connect to the AC if it has a different software version than the AC?

A.     Yes.

Q.     Why can't I configure an auto AP?

A.     An auto AP does not have an AP view and cannot be configured. To configure auto APs, you must convert auto APs to manual APs by executing the wlan auto-ap persistent all command.

Q.     Do fit APs save configuration? How do I upgrade a large number of fit APs in batch?

A.     Fit APs do not save configuration deployed by the AC but save settings configured on the APs. APs automatically upgrade their software versions when connecting to an AC if software upgrade is enabled (default).

Q.     Can ACs provide services to wired users?

A.     Yes.

Q.     How many AC IP addresses does a fit AP support in Option 43?

A.     A fit AP supports a maximum of 16 AC IP addresses in Option 43.

Q.     Can an AP work in fat AP mode?

A.     No. An AP can only work in fit AP mode.

Q.     How can I view the software version of a fit AP?

A.     The software versions of fit APs are saved on the AC. An AP automatically upgrades its software version when connecting to the AC if software upgrade is enabled.

Software upgrade for an AP proceeds as follows:

1.     The AP reports the software version and AP model information to the AC.

2.     The AC examines the received AP software version.

¡     If a match is found in the APDB, the AC establishes a CAPWAP tunnel with the AP.

¡     If no match is found in the APDB, the AC sends a message that notifies the AP of AP software version inconsistency.

3.     Upon receiving the message, the AP requests a software version from the AC.

4.     The AC assigns the software version to the AP after receiving the request. By default, the AC assigns the software version in the memory to the AP. You can configure the AC to assigns the software version in the specified folder.

5.     The AP upgrades the software version, and restarts to establish a CAPWAP tunnel with the AC.

Access controllers (ACs)

This section contains the most frequently asked questions about ACs.

Q.     What are the functions of an AC?

A.     An AC is a wireless switch that can provide management and forwarding functions. It can provide client management functions, such as access control and authorization, and AP management functions, such as association, channel selection, and transmit power control.

An AC can also provide additional functions, including traffic classification and marking, QoS functions such as forwarding priority, and multicast services.

Q.     How can I connect a fit AP to an AC physically?

A.     You can connect an AP to an AC directly or over a Layer 2 network or a Layer 3 network, as long as they can reach each other.

Q.     How does an AC communicate with a fit AP?

A.     An AC and an AP establish a data tunnel to forward data packets, and they establish a control tunnel to forward control packets for AP configuration and management.

After an AP starts up without any configuration and is associated with an AC, the AC assigns configuration to the AP. The AP operates with the assigned configuration and is managed by the AC.

Q.     Can an AC act as a local DHCP server?

A.     Yes.

Q.     How can I view detailed information about manual APs and online auto APs on an AC?

A.     Execute the display wlan ap name ap-name verbose command.

Q.     How can I view the association status of APs on an AC?

A.     Execute the display wlan ap all command. APs in R state have been associated with the AC. APs in I state have not been associated with the AC.

Q.     How can I view the version of an AC?

A.     Execute the display version command.

Q.     How can I view channel information on an AC?

A.     Execute the display wlan rrm-status ap all command.

Q.     How can I separate services of different APs with the same SSID?

A.     To separate services of different APs with the same SSID, execute the service-template service-template-name vlan vlan-id command to assign clients accessing different radios to different VLANs.

Q.     Can I log off a client?

A.     Yes. You can execute the reset wlan client { all | mac-address mac-address } command to log off all or the specified clients.

Q.     What's the difference between the online time and the system up time in the output from the display wlan ap name verbose command?

A.     The output from the display wlan ap name verbose command is shown as follows:

<Sysname> display wlan ap name ap1 verbose

AP name                       : ap1

AP ID                         : 1

AP group name                 : default-group

State                         : Run

Backup Type                   : Master

Online time                   : 0 days 1 hours 25 minutes 12 seconds

System up time                : 0 days 2 hours 22

Online time shows the duration that the AP has been associated with the AC.

System up time shows the duration that the AP has operated since the most recent startup.

Q.     How can I view information about APs that went offline recently on an AC?

A.     Execute the display wlan ap connection record all command. APs that went offline most recently come first in the output. The command output is shown as follows:

<AC> display wlan ap connection record all

AP name          IP address      Serial ID          State     Time              

--------------------------------------------------------------------------------

ap71             7.7.7.41        219801A0T78156A001 Run       2016-04-05 15:27:39

                                 19

Q.     Which UDP ports does a CAPWAP tunnel use?

A.     An AC uses UDP ports 5246 and 5247 for the control tunnel and data tunnel, respectively.

An AP uses random UDP ports for the control tunnel and data tunnel.

Q.     Why can't I view newly created manual APs in the system-defined AP group?

A.     APs in the system-defined AP group are not displayed because all APs belong to the system-defined AP group by default.

Q.     Does an AC support backup?

A.     Yes. ACs support star-topology IRF and other backup methods.

Q.     Do ACs support IRF? How many ACs does an IRF fabric support?

A.     Support for IRF varies by device model.

Table 1 Support for IRF

Series

Model

IRF

Max. number of ACs in an IRF fabric

WX3800H series

WX3820H

WX3840H

Supported

2

 

Q.     How can I configure clients to automatically access another WLAN when the uplink of the associated AC is down?

A.     Enable the AC uplink detection function.

Q.     Do ACs support third-party APs?

A.     No.

Q.     What are the advantages of local forwarding? When do I need to configure local forwarding?

A.     In local forwarding mode, APs directly forward client packets instead of transferring all packets to the AC. This reduces the AC's load. You can specify a VLAN or a VLAN range to enable APs to forward client data traffic from the specified VLANs.

For example, in a branch+headquarters network where the AC is deployed at the headquarters and APs are deployed in branches, you can configure local forwarding as a best practice.

Licenses

This section contains the most frequently asked questions about licenses.

Q.     How do I increase the number of APs that an AC can manage?

A.     Purchase a license.

Q.     How do I know which features require licenses?

A.     Execute the display license feature command to display brief license information for features.

Q.     How can I register and activate a license?

A.     After purchasing a license from H3C, access http://www.h3c.com/cn/License to register your license. For more information about activating a license on the device, see Managing licenses in H3C Access Controllers Fundamentals Configuration Guide.

Q.     How can I view the remaining days of AP licenses?

A.     Execute the display license command. The output from this command is displayed as follows:

<AC> display license

Slot 1:

cfa0:/license/210235A1AMB1570000052015091410025584386.ak

Feature: APMGR

Product Description: Enhanced Access Controller License,128 APs,for Verticals,for V7

Registered at: 2015-09-14 10:04:09

License Type: Trial (days restricted)

Trial Time Left (days): 353

Current State: In use

Q.     How can I view the number of AP licenses?

A.     Execute the display wlan ap all command. The output from this command is displayed as follows:

<AC> display wlan ap all

Total number of APs: 1

Total number of connected APs: 1

Total number of connected manual APs: 1

Total number of connected auto APs: 0

Total number of connected common APs: 1

Total number of connected WTUs: 0

Total number of inside APs: 0

Maximum supported APs: 1024

Remaining APs: 1023

Total AP licenses: 128

Local AP licenses: 128

Server AP licenses: 0

Remaining local AP licenses: 127

Sync AP licenses: 0

                             AP information

State : I = Idle,         J = Join,        JA = JoinAck,         IL = ImageLoad

        C = Config,       DC = DataCheck,  R = Run M = Master,   B = Backup

AP name        APID       State       Model          Serial ID

ap1            1          R/M         WA538          219801A1NN9182032213

Q.     Do I need to restart the device for the license to take effect after installing a license?

A.     No. A license takes effect immediately after it is installed.

Q.     Will the installed licenses be deleted when the file system is formatted?

A.     No. The installed licenses will not be deleted if the file system is formatted from the CLI or the BootWare menu.

Q.     Can I edit a license file?

A.     No. Do not modify the name of a license file to avoid licensing error, and do not edit a license file to avoid file corruption.

Q.     In an IRF fabric, how does the use of licenses change after a member AC leaves the fabric?

A.     An IRF fabric uses the licenses installed on each member AC. If a member AC leaves the IRF fabric, the IRF fabric can use the license installed on the AC for only 30 days.

Networking

This section contains the most frequently asked questions about networking.

Q.     How is an AP associated with an AC in different fit AP+AC networking environments?

A.     An AP can be associated with an AC in direct mode, Layer 2 mode, or Layer 3 mode:

·     Direct mode and Layer 2 mode—The IP addresses of the AC and AP are in the same subnet.

·     Layer 3 mode—The IP addresses of the AC and the AP are in different subnets.

Q.     At which layer can I deploy an AC in a fit AP+AC network?

A.     An AC can be deployed at the core layer or the aggregation layer. You can connect a fit AP to an AC directly or through an existing wired network. User preference, AP density, and the role of the WLAN in the whole network can affect the location of the AC in the network topology.

Q.     Do I need to change the wired backbone network for WLAN devices?

A.     No.

Q.     How are packets forwarded by default in a fit AP+AC network?

A.     All ACs use the centralized forwarding mode by default.

WLAN security

This section contains the most frequently asked questions about WLAN security.

Q.     Which authentication methods does an AC support?

A.     An AC supports the following authentication methods:

·     802.1X authentication.

·     PSK authentication.

·     MAC address authentication.

·     Portal authentication.

·     PPPoE authentication.

Q.     Can I configure local forwarding and centralized authentication at the same time when portal authentication is used?

A.     Yes.

Q.     Does an AC support portal authentication?

A.     Yes.

Q.     Can an AC cooperate with a third-party LDAP server for authentication?

A.     Yes. An AC can cooperate with common LDAP servers, including the Active Directory Server of Microsoft, the Tivoli Directory Server of IBM, and the Sun ONE Directory Server of Sun.

Q.     In a wireless network, which device acts as an AAA authenticator?

A.     In a wireless network, the AC is the AAA authenticator. You only need to configure the AC, instead of each AP, as the AAA client. This feature reduces network configuration load and operating costs.

Q.     Can an AC detect rogue APs?

A.     Yes. An AC can detect rogue devices when Wireless Intrusion Prevention System (WIPS) is configured.

WLAN roaming

This section contains the most frequently asked questions about WLAN roaming.

Q.     What is WLAN roaming? How many types of WLAN roaming are available?

A.     WLAN roaming enables wireless clients to roam between APs in the same Extended Service Set (ESS), keeping their original IP address and privileges unchanged.

WLAN roaming includes the following types:

·     Intra-AC roaming—Roaming among APs managed by the same AC.

·     Inter-AC roaming—Roaming among APs managed by different ACs.

Q.     Can wireless clients perform Layer 3 roaming?

A.     Yes.

Q.     Do clients need to be reauthenticated or log in again after roaming?

A.     No.

Q.     During WLAN roaming, will a client keep its subnet attributes such as the assigned VLAN, ACL, and routing policies?

A.     Yes. All subnet attributes remain the same during WLAN roaming, including the assigned VLAN, ACL, priority, and other policies.

Q.     Does the IP address of a client remain unchanged during WLAN roaming?

A.     Yes.

Q.     How can I adjust the sensitivity of a wireless NIC?

A.     Adjust the roaming sensitivity level of the wireless network card.

Q.     Do I need to change the switch or router configuration to enable WLAN roaming?

A.     No.

Q.     Do I need to install new client software for WLAN roaming?

A.     No.

System management

This section contains the most frequently asked questions about system management.

Q.     Can I configure a mandatory rate for an AC to increase the wireless network performance?

A.     Yes. If the network is not in good condition, you can configure the AC to use the mandatory rate (the maximum rate) to transmit data. This method can increase the bandwidth and network performance. To configure a mandatory rate, use the rate { multicast { auto | rate-value } | { disabled | mandatory | supported } rate-value } command.

Q.     How can I determine whether memory leakage has occurred?

A.     Execute the display memory command. If the free ratio decreases gradually and cannot recover automatically, memory leakage might have occurred. The output from the command is shown as follows:

<Sysname> display memory

Memory statistics are measured in KB:                                          

Slot 1:                                                                        

             Total      Used      Free    Shared   Buffers    Cached   FreeRatio

Mem:       3775116   2415348   1359768         0      2544    628524       36.0%

-/+ Buffers/Cache:   1784280   1990836                                         

Swap:           0         0         0

Q.     How can I view process state information?

A.     Execute the display process command.

Q.     How can I view memory usage for all processes?

A.     Execute the display process memory command.

IRF

This section contains the most frequently asked questions about IRF.

Q.     Is there an upper limit on the number of member devices of an IRF fabric?

A.     Yes. If the number of member devices in an IRF fabric reaches the limit, no more devices can join the fabric.

Q.     Does an IRF fabric have requirements on the software versions of its member devices?

A.     All member devices in an IRF fabric must have the same software version. If devices with different software versions are to be added to an IRF fabric, make sure the software auto-update feature is enabled.

Q.     Are there any requirements on IRF bridge MAC addresses when two IRF fabrics merge?

A.     For a successful IRF merge, make sure the two IRF fabrics have different IRF bridge MAC addresses.

Q.     Do I need to disable STP on switch interfaces when member devices are connected through a Layer 2 network?

A.     Yes.

Q.     Under what circumstances do I need to use a switching device to form a star-topology IRF fabric?

A.     If the IRF fabric contains only two member devices, you can connect the member devices directly or through a Layer 2 network. If the IRF fabric contains more than two member devices, you must use a switching device to connect them.

Q.     What restrictions and guidelines do I need to follow after an IRF fabric is formed?

A.     When you use an IRF fabric, follow these restrictions and guidelines:

·     To avoid IRF split, do not use the shutdown command on an IRF network interface if the interface is the only control channel available on the IRF standby device.

·     IRF uses an IRF domain ID to uniquely identify an IRF fabric. Devices must have the same IRF domain ID to form an IRF fabric.

·     In a star-topology IRF fabric that has cross-card aggregation links, do not set the link-aggregation load sharing mode to per-packet.

·     NAT is not supported in an IRF fabric.

·     If multiple physical IRF links operate correctly between two devices, shut down all interfaces on both devices before you remove an IRF link.