Vlan trunk and average CPU

Unanswered Question
Jun 2nd, 2010

Hello,

I set a vlan trunk between 2 switches. the first switch is a 3750 and the second one a 2960 (24TS-S). I don't use VTP, I enter this command on the 2960 for the trunk port : switchport mode trunk. The VLAN propogation works fine but the switch as an average CPU of 50% as soon as I enter the command. I think 50% as average is not normal. This is not a trafic problem, there is no devices connected to the 2960 yet.


sh process CPU sort

CPU utilization for five seconds: 7%/1%; one minute: 42%; five minutes: 49%
PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
  96       39974      8447       4732  0.49%  0.47%  0.47%   0 hpm counter proc
  58       13245     31017        427  0.39%  0.20%  0.13%   0 RedEarth Tx Mana
254          26       119        218  0.19%  0.03%  0.00%   1 Virtual Exec
  10       24261    139934        173  0.09%  0.17%  0.26%   0 ARP Input
131        8927      1722       5184  0.09%  0.09%  0.09%   0 HQM Stack Proces
   6           0         2          0  0.00%  0.00%  0.00%   0 Timers
   5           0         1          0  0.00%  0.00%  0.00%   0 Pool Manager
   8       14108       143      98657  0.00%  0.16%  0.12%   0 Licensing Auto U
   4       12557      1314       9556  0.00%  0.12%  0.11%   0 Check heaps
   7           0         1          0  0.00%  0.00%  0.00%   0 License Client N
   9           0         1          0  0.00%  0.00%  0.00%   0 Image License br

sh process history

    7777777666668888866666666668888877777666666666677777777777
100
90
80
70
60
50
40
30
20
10 **********************************************************
   0....5....1....1....2....2....3....3....4....4....5....5....
             0    5    0    5    0    5    0    5    0    5
               CPU% per second (last 60 seconds)

    5555555555555555555556555555555555555555555555555555555555
    5253543447453435444442444346665554446644454445466445466444
100
90
80
70
60 * * *    * *   *     *     ******   **   *   * **  * **
50 *#########################################################
40 *#########################################################
30 ##########################################################
20 ##########################################################
10 ##########################################################
   0....5....1....1....2....2....3....3....4....4....5....5....
             0    5    0    5    0    5    0    5    0    5
               CPU% per minute (last 60 minutes)
              * = maximum CPU%   # = average CPU%

    65
    29
100
90
80
70
60 **
50 ##
40 ##
30 ##
20 ##
10 ##
   0....5....1....1....2....2....3....3....4....4....5....5....6....6....7.
             0    5    0    5    0    5    0    5    0    5    0    5    0
                   CPU% per hour (last 72 hours)
                  * = maximum CPU%   # = average CPU%

What do you think ? You should I worry ?

Thanks for your help.

Chris
I have this problem too.
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Calin Chiorean Wed, 06/02/2010 - 05:23

How come you are not using VTP? You mean by that the VTP mode is transparent?

What VLANs are configured on the 2 switches? Also check with

show interface x/y switchport

that the 2 ports connected are having similar configuration.

Please give us more details to be able to help.

Calin

sysadminicm Wed, 06/02/2010 - 08:04

Thanks for your quick reply Calin

I don't use VTP because I'm not coming from a Cisco world and I thought it would be easier no to create a VTP domain since I need this trunk only for a while. I didn't change any VTP settings applied on the 2960 so the default settings applied, I'm not sure about the 3750, I didn't install the switch my self and I'm a Cisco newbie.

But may be I'm wrong and setting a VTP domain is not that hard.

So is the result of sh interfaces x switchport

for the 2960

Name: Gi0/25

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Administrative Native VLAN tagging: enabled

Voice VLAN: none

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk Native VLAN tagging: enabled

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk associations: none

Administrative private-vlan trunk mappings: none

Operational private-vlan: none

Trunking VLANs Enabled: ALL

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

Protected: false

Unknown unicast blocked: disabled

Unknown multicast blocked: disabled

Appliance trust: none

VTP status :

VTP Version capable             : 1 to 3
VTP version running             : 1
VTP Domain Name                 :
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Disabled
Device ID                       : 1c17.d3e2.7400
Configuration last modified by 101.10.5.91 at 3-1-93 01:27:18
Local updater ID is 101.10.5.91 on interface Vl1 (lowest numbered VLAN interface found)

Feature VLAN:
--------------
VTP Operating Mode                : Server
Maximum VLANs supported locally   : 64
Number of existing VLANs          : 6
Configuration Revision            : 1
MD5 digest                        : 0xF3 0x96 0x2E 0x43 0xD4 0x98 0xF1 0x6B
                                    0x98 0x33 0xFB 0x2E 0xF7 0x05 0x7A 0xDB

for the 3750

Name: Gi1/0/13
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL

Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

VTP status

VTP Version                     : 2
Configuration Revision          : 3
Maximum VLANs supported locally : 1005
Number of existing VLANs        : 8
VTP Operating Mode              : Server
VTP Domain Name                 :
VTP Pruning Mode                : Disabled
VTP V2 Mode                     : Disabled
VTP Traps Generation            : Disabled
MD5 digest                      : 0xB9 0x69 0x6A 0xFE 0xCE 0x92 0x0A 0x24
Configuration last modified by 101.10.5.51 at 8-19-09 13:16:31
Local updater ID is 101.10.5.51 on interface Vl1 (lowest numbered VLAN interface found)

Chris

Calin Chiorean Wed, 06/02/2010 - 08:15

OK, let me help you a little bit to see if the CPU goes down.

First, I don't know if this is productive environment or not, but if it is, then you have to take care not to interrupt any services.

1. Create the same Vlans on both Cisco switches

enable

conf t

vlan xxx

2. Configure hard trunking on both switches like:

enable

conf t

interface x/x

switchport trunk encapsulation dot1q

switchport mode trunk

swichport trunk allow vlan all

switchport nonegotiate

-in this way you ensure that autonegotiation is off, and both interfaces are in trunk mode

3. Configure VTP

enable

conf t

vtp version 2

vtp mode transparent

vtp domain "something"    -> where something can be whatever you want, but still to somehow reflect your domain

VTP transparent will eliminate the negotiation like in the Server mode, how it is now.

Try and let me know if it's working.

If you find this useful please rate.

P.S. Again pay attention if productive environment, and if you have concerns let me know.

sysadminicm Thu, 06/03/2010 - 00:28

Calin,

This is a production environment, does the VTP settings on the 3750 can interrupt any services ?

sysadminicm Thu, 06/03/2010 - 08:08

I thought I got the solution, I didn't enter the NTP server IP address properly. I made the correction than the CPU average load stayed at 7% for 50 minutes then up to 50% again, grr.

When I do a "sh process CPU sort", I can't see which process is causing trouble. Why ?

Chris

sysadminicm Fri, 06/04/2010 - 08:09

Update :

I reset the switch configuration and I still have 50% average CPU. If I enter a command like "sh run" for instance, the cpu% dropped than after a while up again to 50%. I really don't undestand, I can't see any process causing trouble with "sh process cpu sort".

Any ideas ?

Thanks.

Chris

sysadminicm Tue, 06/08/2010 - 03:44

I close this topic since it's not  related exactly related to vlan trunk and I'll open a new one.

Chris

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