Broadcast

[Robo123]

Hi Team,

I have cisco 7609,7606 where we are observing huge broadcast packets so i want to know possible  ways to limit broadcast packets and interrupts.

Please share the valid cisco document for the same .

[Georg Pauwen]

Hello,

storm control can be configured on individual interfaces, as in the example below:

7609# configure terminal
7609(config)# interface gigabitethernet 1/1
7609(config-if)# storm-control multicast level 40
7609(config-if)# end

Check the document below for reference. Obviously it is imperative to locate the source of the excessive broadcasts...

https://www.cisco.com/c/en/us/td/docs/routers/7600/ios/15S/configuration/guide/7600_15_0s_book/storm.html

[Robo123]

Hi Georg,

Thanks for the replay.

As per document

When multicast suppression is enabled, traffic storm control suppresses BPDUs when the multicast suppression threshold is exceeded on these modules:

– WS-X6748-SFP

– WS-X6724-SFP

– WS-X6748-GE-TX

– WS-X6748-GE-TX

– WS-X6704-10GE

– WS-SUP32-GE-3B

– WS-SUP32-10GE-3B

When multicast suppression is enabled on the listed modules, do not configure traffic storm control on STP-protected ports that need to receive BPDUs. Except on the listed modules, traffic storm control does not suppress BPDUs.

1)which means if the multi cast Traffic is exceeding the threshold then the port will go for error disable mode?

2)I am using WS-X6748-GE-TX line card where i am getting huge broadcast packet intermitantly.so i want to know once I am configuring threshold for “ storm-control broadcast level” will help to reduce the huge broadcast packet flow.

Please clarify the above.

[Robo123]

Currently we have configured the storm-control as per the above document. but still broadcast storm punts Router CPU. Please help and share the appropriate value of storm-control level so that it will not impact router CPU.

Please share the document as well. 

[Georg Pauwen]

Hello,

try and set the level to 10.00:

storm-control broadcast level 10.00

[Robo123]

Currently below is our config

storm-control broadcast level 0.10
storm-control multicast level 0.10

but still we are getting lot of broadcast packet so onec it changing to 

storm-control broadcast level 10.00

issue will get resolve or not ?

[Robo123]

Hi Gorge,

What is the significate of this below command:

mls qos protocol ARP police 512000 16000

[paul driver]

Hello

Broadcast traffic on a interface can be actually multicast traffic or both.

Can you elaborate on what you are experiencing - you also mention interrupts  would this be the cpu process.% interrupt?

What do the interface and counter statistics show?

sh int xx
sh int xx count

Do you have ip directed broadcast enabled?
Do you have large broadcast domains?
Do you have flow control enabled?

Note: enabling a storm control  level for broadcast and multicast can have an effect both traffic even if only one or the other reaches it define limit.

res
Paul

[Robo123]

Hi Paul,

Please help me to now what the below command will do and what is this <value> parameeter need to configure the below.

snmp-server enable traps storm-control trap-rate value

mls qos protocol arp police 64000 1000.

explain Value indicates what for both commnand.

[Joseph W. Doherty]

"huge broadcast packets"

Huge as in size of packets or huge as in volume in a short time?

Broadcast traffic is often "normal" and needed for correct network operations. Using storm control can suppress such valid traffic. However, sometimes it's needed to keep a network (somewhat) operational when there's a large batch of broadcast traffic.

If you believe you have large batches of broadcast traffic, you should also pursue the cause and try to eliminate it. For example, large batches of valid broadcast traffic might be due to using too large network blocks.