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New Member

Broadcast level


I would like to know how much broadcast, in theory, could be acceptable in a vlan. % ?

Now I have about 15% in a vlan of 400 servers, I'm sure that my MSFC's are supporting it but I'm worried about the servers because I know it's going to grow because of the applications



Re: Broadcast level

Theory (CCDA) says max. 20% of broadcasts/multicasts.



Re: Broadcast level

This is a theoretical maximum, but I would feel more comfortable with values below 10%. When you are already having 15% it should be time to take some measures to reduce broadcast traffic. In my opinion 15-20% should only be a peak value, not a value that should be considered adequate.

One more note: Did you measure the 15% on a time when the network was normally loaded or did you measure during a time when there was little traffic? In the last case, you may have found a value that is too high.



New Member

Re: Broadcast level


I've measured it in normal operation, there are 10 servers using broadcast to talk each other, but they carry a lot of traffic. Here you can see the statistics of the interface vlan.

I supposed we are going to separate it from the main vlan.

Hardware is EtherSVI, address is 0008.20b4.fc0a (bia 0008.20b4.fc0a)

Description: vlan CPD2 (HP,SUN)

Internet address is

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 5w3d

Input queue: 0/75/41561/35 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 4282000 bits/sec, 1341 packets/sec

5 minute output rate 7000 bits/sec, 23 packets/sec

L2 Switched: ucast: 22907979682 pkt, 21235593209893 bytes - mcast: 377252208 p

kt, 70731867370 bytes

L3 in Switched: ucast: 2093449161 pkt, 690426281460 bytes - mcast: 483 pkt, 86

404 bytes mcast

L3 out Switched: ucast: 1439645483 pkt, 290999082385 bytes

2542524191 packets input, 495290120 bytes, 0 no buffer

Received 373015869 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

157645258 packets output, 1042250232 bytes, 0 underruns

0 output errors, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

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