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Community Member

Cisco 4500 High CPU Utilization (storm control broadcast)

Hello All,

i have a network setup operational, have one Cisco Core Switch (4506-E) with SUP 7 engine (WS-X45-SUP7-E). Three modules are 48 Port 1G SFP Ports (WS-X4448-GB-SFP).

Have 130+ access switches (cisco 2960). All the access switches are connected to the Core Switch mentioned above using 1G fiber ports.

CPU utilization has been going high and whenever it goes high, reason is "ARP Input" usually at the peak time, if i do "show process cpu detailed ", it shows "ARP Input" under "iosd" which has a higher percentage.

On access switches i have configured storm contro broadcast configuration on interfaces but it has not been effective in putting those interfaces in an err-disabled state who send too many broadcast packets.

int range fastEthernet 0/1 - 48

description ##TO-END-USERS##

switchport mode access

switchport access vlan 10

speed auto

duplex auto

spanning-tree portfast

spanning-tree bpdufilter enable

no shut

no ip dhcp snooping trust

ip dhcp snooping limit rate 70

storm-control broadcast level 30.00 10.00

storm-control action shutdown

exit

i want to change the value of broadcast levels and use pps value instead of %age, but not sure of how to get a correct number of setting these levels

need help in modifying the storm control configuration.

3 REPLIES

Cisco 4500 High CPU Utilization (storm control broadcast)

I'm not sure how to convert percentage to pps for you, but 30 percent seems kind of high to me per port. I use 5 percent on my edge switches and it seems fine. Your telling the switch that it needs to hit 30Mb of broadcast traffic before it will shut the port. 30Mb on 100Mb port seems excessive to me anyway. If you have a gig uplink, you would need 33 hosts sending 30Mb of broadcast to saturate your uplink which leaves you with 15 hosts on this switch that can't do anything (aside from the already existing broadcast storm).

If you have a 100Mb uplink, then the problem is even worse since now you technically can't have more than 3 hosts to saturate your uplink not considering the other hosts with normal traffic.

HTH,
John

*** Please rate all useful posts ***

HTH, John *** Please rate all useful posts ***
Community Member

Cisco 4500 High CPU Utilization (storm control broadcast)

thank you for the suggestion..

all access switches has gig uplinks to the core,

you set 5 percent as a higher threshold value or lower ?

Cisco 4500 High CPU Utilization (storm control broadcast)

I set it as the upper limit and then anything under would be an acceptable value. I have a pretty busy access layer, and with 5 percent, I rarely get storm control messages.

HTH,
John

*** Please rate all useful posts ***

HTH, John *** Please rate all useful posts ***
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