- Introduction
- Core Issue
- Resolution
- Examples
- Problem Type
- Products
- Topology
- Product OS
- Link Status Meter Test Result
- Wireless Stages
- Reference
Introduction
High CPU utilization on Access point, loopback interface configured on AP
Core Issue
Users will see the following symptoms in the Wireless network when loopback interfaces are configured on APs
- When logging onto the AP via telnet, response is slow, and CPU usage is high.
- One can notice a process consuming the CPU is AiroIAPP Protocol, showing as high cpu usage as compared to other process CPU usage.
- Sometime the AP dose not respond to pings for a period of around 5 minutes.
Resolution
Causes:
Check for the following if you have high CPU
- High CPU might be the result of an IAPP GENINFO storm on the network, which happens if the Access Points (AP) have loopback interfaces configured on them. It is advised that one should remove the loopback interfaces if configured on the AP in order to avoid the IAPP GENINFO storm on the network. This particular issue is also referenced in the release notes, and also found it in the command reference, for information on this refer to Caution statement in the IOS Command Reference Guide.
Caution 
Access points and bridges do not support the interface loopback command. Configuring a loopback interface might generate an IAPP GENINFO storm on your network.
- If the access point is connected to the switch port make sure the switchport which is connected to the access point is pruned to allow VLANs that the access point is interested . This reduces the un-necessary trafiic being sent to the access point from the wired network through the switch thereby increasing the access point CPU. Refer Switch Configuration for more information.
Switch Configuration—Catalyst OS
In order to configure a switch that runs Catalyst OS to trunk VLANs to an access point, the command syntax is set trunk <module #/port #> on dot1q and set trunk <module #/port #> <vlan list>.
An example from to the sample network diagram, is:
set trunk 2/1 on dot1q set trunk 2/1 1,10,30
Switch Configuration — IOS Based Catalyst Switches
From interface configuration mode, enter these commands, if you want to:
- Configure the switchport to trunk VLANs to an access point
- On a Catalyst switch that runs IOS
- The CatIOS includes but is not limited to:
- 6x00
- 4x00
- 35x0
- 295x
switchport mode trunkswitchport trunk encapsulation dot1qswitchport nonegotiateswitchport trunk native vlan 1switchport trunk allowed vlan add 1,10,30
Note: IOS based Cisco Aironet wireless equipment does not support Dynamic Trunking Protocol (DTP), so the switch must not try to negotiate it.
Switch Configuration—Catalyst 2900XL/3500XL
From interface configuration mode, enter these commands, if you want to configure the switchport to trunk VLANs to an access point on a Catalyst 2900XL or 3500XL switch that runs IOS:
switchport mode trunkswitchport trunk encapsulation dot1qswitchport trunk native vlan 1switchport trunk allowed vlan 1,10,30
- Based on the additional features configured on the access point amount of CPU relatively increases. For example if access point is configured as WDS as well as serves the wireless clients this happens.
- Sometimes management stations might flood the access point as a part of of SNMP polling and configuration. Make sure management traffic is in control
As a workaround try to reboot the access point. If this doesn't help Upgrade the IOS as a last resort. Backup the configuration before upgrade is done.
To interpret the access point CPU utilization refer show processes cpu . You can also use Show tech command to check the memory status.
Use the show processes EXEC command to display information about the active processes.
show processes [cpu]
Syntax Description
cpu | (Optional) Displays detailed CPU utilization statistics. |
Command Modes
EXEC
Command History
Modification
10.0 | This command was introduced. |
Examples
The following is sample output from the show processes command:
Router# show processes
CPU utilization for five seconds: 21%/0%; one minute: 2%; five minutes: 2%
PID QTy PC Runtime (ms) Invoked uSecs Stacks TTY Process
1 Mwe 2FEA4E 1808 464 3896 1796/3000 0 IP-EIGRP Router
2 Lst 11682 10236 109 93908 1828/2000 0 Check heaps
3 Mst 3AE9C 0 280 0 1768/2000 0 Timers
4 Lwe 74AD2 0 12 0 1492/2000 0 ARP Input
5.ME 912E4 0 2 0 1892/2000 0 IPC Zone Manager
6.ME 91264 0 1 0 1936/2000 0 IPC Realm Manager
7.ME 91066 0 30 0 1784/2000 0 IPC Seat Manager
8.ME 133368 0 1 0 1928/2000 0 CXBus hot stall
9.ME 1462EE 0 1 0 1940/2000 0 Microcode load
10 Msi 127538 4 76 52 1608/2000 0 Env Mon
11.ME 160CF4 0 1 0 1932/2000 0 MIP Mailbox
12 Mwe 125D7C 4 280 14 1588/2000 0 SMT input
13 Lwe AFD0E 0 1 0 1772/2000 0 Probe Input
14 Mwe AF662 0 1 0 1784/2000 0 RARP Input
15 Hwe A1F9A 228 549 415 3240/4000 0 IP Input
16 Msa C86A0 0 114 0 1864/2000 0 TCP Timer
17 Lwe CA700 0 1 0 1756/2000 0 TCP Protocols
18.ME CCE7C 0 1 0 1940/2000 0 TCP Listener
19 Mwe AC49E 0 1 0 1592/2000 0 BOOTP Server
20 Mwe 10CD84 24 77 311 1652/2000 0 CDP Protocol
21 Mwe 27BF82 0 2 0 1776/2000 0 ATMSIG Input
Problem Type
The signal is weak or fluctuating
High CPU load
Products
Autonomous Access Points
Topology
Wireless client to AP
Product OS
IOS
VxWorks
Link Status Meter Test Result
Fair
Poor
Wireless Stages
Authenticated and Associated
Reference