HL3U bkgrd proce high CPU usage in 3750X switch

[julio.aldana]

Hello

The process "HL3U bkgrd proce" is causing high CPU usage issues in a switch 3750X-24T-L. The IOS is

15.0.2-SE2.

show platform ip unicast failed route and adjacencies displays a lot of entries, I've seen up to 1200.

After restart HL3U bkgrd proce takes around 10 - 20 % CPU, some hours later 99%.

A coupe of times we got logs like this:

%SYS-3-CPUHOG: Task is running for (2136)msecs, more than (2000)msecs (172/73),process = HL3U bkgrd process.

-Traceback= 0x1BE9C3Cz 0x27E103Cz 0x27E0F64z 0x50DCF8z 0x50DE98z 0x503BD0z 0x4F7718z 0x1FF0A18z 0x1F46DECz 0x1F4816Cz 0x1F48698z 0x1F499C8z 0x1FF15D0z 0x2000430z 0x1FF55B4z 0x1FF5FA4z

which desapear after restart.

also

%SYS-3-MGDTIMER: Uninitialized timer, init with uninitialized master, timer = 47327A8. -Process= "Init", ipl= 0, pid= 4

-Traceback= 4FCA14z 1C3A44Cz 85C464z 1C43F94z 1C44154z 1C44270z 50C180z 50C378z 26BF904z 26BA058z

at startup.

Could this be caused by too high L3 traffic? We have only 3 VLAN with about 300Mbps of traffic. We have a very simple configuration, without routing protocols or policies. Just a single static route and inter-VLAN routing (3 vlans directly connected)..

I would appreciate any help.

Thanks.

[acampbell]

Julio,

You may have an excessive ARP issue

CSCef37743 Bug Details

high cpu with ARP input and HL3U bkgrd process

Symptom: Cisco Catalyst 3750 and 3560 switches will show high CPU utilization in the HL3U process when running Cisco IOS 12.2(18)SE through 12.2(20)SE2 with a large number of proxy ARP entries. In some rare conditions, the switch may reload.Conditions: This problem is observed on Catalyst 3750 and 3560 switches running 12.2(18)SE through 12.2(20)SE2 with a large number of proxy ARP entries.Further Problem Description: The command show platform ip unicast proxy will show the number of proxy ARP entries.In some cases, debug arp may show that interfaces are receiving a large number of invalid arp requests/replies

Regards,
Alex.
Please rate useful posts.

[InayathUlla Sharieff]

Hi,

Hl3u bkgrd process - manages quite a few background tasks like

- Hardware Arp throttling house keeping tasks

- Retry adjs/Fib in case of an out of hardware resource condition

- proxy arp house keeping functions

- ICMP redirect processing

- TTL ICMP error generation in some conditions

- handling correct route forwarding in an output acl full condition

2) Check for ARP statictics under sh ip traffic.I dont have any access to the config of your device hence assuming.

could you check if "no ip arp incomplete enable" command dose the trick for you?

3) Also consider the bug mentioned by Alex thats a clean hit.

HTH

Regards

Inayath