topic RE: command show the broadcast? in Network Architecture & Design

command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 16:30:00 GMT

Dears, Whish the good way to show my if the my switch have be broadcast? Im using extreme switches in my network type summit 450x dc

RE: command show the broadcast?

Chad_Smith1 — Thu, 17 Mar 2016 18:22:00 GMT

Munir,

The "show port PORT_NUMBER statistics" command will give you a count of tx/rx broadcast packets.

Switch.4 # show port 1-8 statistics Port Statistics Thu Mar 17 08:19:14 2016
Port Link Tx Pkt Tx Byte Rx Pkt Rx Byte Rx Pkt Rx Pkt Tx Pkt Tx Pkt
State Count Count Count Count Bcast Mcast Bcast Mcast
========= ===== =========== =========== =========== =========== =========== =========== =========== ===========
1 A 86778262 >9999999999 44798438 >9999999999 261282 1785058 2564427 4508394
2 A 678633371 >9999999999 207442932 >9999999999 1969144 1470118 856589 5897837
3 A 85002332 >9999999999 79851935 >9999999999 321432 512860 2504116 4139455
4 A 34737253 4699692162 356078012 >9999999999 3560 158728 2816932 7017579
5 A 246080952 >9999999999 335156100 >9999999999 77787 3994862 2747848 682118
6 R 0 0 0 0 0 0 0 0
7 R 0 0 0 0 0 0 0 0
8 A 176840632 >9999999999 252394779 >9999999999 138236 52472 2687108 6341237

========= ===== =========== =========== =========== =========== =========== =========== =========== ===========
> in Port indicates Port Display Name truncated past 8 characters
> in Count indicates value exceeds column width. Use 'wide' option or '0' to clear.
Link State: A-Active, R-Ready, NP-Port Not Present L-Loopback
0->Clear Counters U->page up D->page down ESC->exit

RE: command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 18:22:00 GMT

Thank you. But which number infirred on brodcast?

RE: command show the broadcast?

Chad_Smith1 — Thu, 17 Mar 2016 18:22:00 GMT

Munir the 7th column "Rx Pkt Bcast" (in bold) is the number of broadcast packets received on the port. The 9th column "Tx Pkt Bcast" (also in bold) is the number of broadcast packets transmitted by the port.

RE: command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 18:22:00 GMT

I am grateful to you, in below image the value when i did show ports statistic ?

that's mean i have some thing wrong in my switch?

RE: command show the broadcast?

Chad_Smith1 — Thu, 17 Mar 2016 18:22:00 GMT

Munir,

In your snapshot the broadcast counters are fairly low, so unless you had just cleared the counters I do not think there is an issue with broadcast traffic on the network. Even still, it is a small amount proportional to the total traffic on the port. I don't think you have a problem.

However, I must say that it is difficult to determine from a snapshot of the command. When you are suspecting a problem with broadcast traffic on your network (i.e. broadcast storm) then you need to look at the rate of broadcast traffic. A sustained transmission of a large amount of broadcast traffic would indicate a potential problem with broadcast traffic. What is a large amount? Well that depends on a lot of factors. Generally, the larger the broadcast domain (more devices in the VLAN) and the larger the number of VLANs on the port the more normal broadcast traffic you will see. Any sustained broadcast of 500-1000 pps on an edge port would probably be something worth investigating.

RE: command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 18:22:00 GMT

grateful. Thank you

RE: command show the broadcast?

BradP — Thu, 17 Mar 2016 18:22:00 GMT

Munir,

When troubleshooting a broadcast storm, I like to use the "show l2stats" command. This will display the number of packets that have gone to the CPU on a per vlan basis. Before running the command, I will issue a "clear counters" command and then "show l2stats" at a known time (4-5 seconds or so). This way I can determine about how many packets per second have gone to the CPU and can determine which vlans are high or not. If there is a standout vlan, I will then use ELRP in order to find out which ports are looped. Hope this helps.

Brad

RE: command show the broadcast?

EtherMAN — Thu, 17 Mar 2016 18:22:00 GMT

Another quick way to find this is to do a show port utilization for switch that is ina broadcast loop and the two ports that are looped together will have RX and TX at 100% .. all other ports will only be TX 100%. Disable either one of those two ports and no more loop... Other thing we do on all newer XOS switches put a rate shape on broadcast packets only ...Access/client ports 100 pps ..... Gig Trunk ports 2000 pps..... ten gig trunk ports 5000 pps... looped port will get slowed down b the rate shape and send a trap ....

RE: command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 18:22:00 GMT

Thanks for the explain Bard , i did your steps as you told me, i would inform you about the results obtained by steps . and please inform me if the result normal or unstable ?

RE: command show the broadcast?

BradP — Thu, 17 Mar 2016 18:22:00 GMT

Munir,

That looks absolutely beautiful. The switch output in that screenshot shows very little actual packets going to the CPU.

RE: command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 18:22:00 GMT

thank dear, but what is the maximum packets coming into the CPU?

RE: command show the broadcast?

BradP — Thu, 17 Mar 2016 18:22:00 GMT

Hi Munir,

I don't quite understand your question. The 'show l2stat' command shows how many packets have gone to the CPU since the last time the 'clear counters' command was run or the switch was rebooted. Earlier in the thread, Chad Smith mentioned that anything over 500-1000 PPS going to the CPU from an edge port is worthy of being investigated. Can you explain your question in more detail?

RE: command show the broadcast?

MUNIR_ENG — Thu, 17 Mar 2016 18:22:00 GMT

That's what I'm asking for you, Thank you for your help.