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Beginner

How many broadcasts are too many broadcasts.

Hello everyone,

1 day and 2 hours ago I cleared the counters on a SVI on a 6509 running IOS.  Since then the interface has received 1386034 broadcasts (89547 IP multicasts).  I have a few questions about the interface's broadcast counter:

1. Is there a magical formula to figure out if there are too many broadcasts occurring on the vlan?

1. What traffic is being counted as broadcasts, is it strictly all F's or all 255'3 or is ARP and HSRP Multicast and other protocols counted as broadcasts? 

I  believe the flooding of broadcasts is filling the interface input queue and causing drops.

Thanks

Erik,,,,,,

VlanXX is up, line protocol is up

  Hardware is EtherSVI, address is 0019.a9f8.f000 (bia 0019.a9f8.f000)

  Description: Business Partner Network

  Internet address is x.x.x.x/x

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

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

  Encapsulation ARPA, loopback not set

  Keepalive not supported

  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 1d02h

  Input queue: 0/4096/917/917 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 33000 bits/sec, 18 packets/sec

  5 minute output rate 4000 bits/sec, 7 packets/sec

  L2 Switched: ucast: 28271274 pkt, 14513790452 bytes - mcast: 1386339 pkt, 104250673 bytes

  L3 in Switched: ucast: 522593 pkt, 511617457 bytes - mcast: 0 pkt, 0 bytes mcast

  L3 out Switched: ucast: 218919 pkt, 17736207 bytes mcast: 0 pkt, 0 bytes

     2271895 packets input, 639427117 bytes, 0 no buffer

     Received 1386034 broadcasts (89547 IP multicasts)

     0 runts, 0 giants, 0 throttles

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

     417206 packets output, 35944753 bytes, 0 underruns

     0 output errors, 0 interface resets

     0 output buffer failures, 0 output buffers swapped out

 

VlanXX is up, line protocol is up
  Hardware is EtherSVI, address is 0019.a9f8.f000 (bia 0019.a9f8.f000)
  Description: Business Partner Network
  Internet address is x.x.x.x/x
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not supported
  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 1d02h
  Input queue: 0/4096/917/917 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 33000 bits/sec, 18 packets/sec
  5 minute output rate 4000 bits/sec, 7 packets/sec
  L2 Switched: ucast: 28271274 pkt, 14513790452 bytes - mcast: 1386339 pkt, 104250673 bytes
  L3 in Switched: ucast: 522593 pkt, 511617457 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 218919 pkt, 17736207 bytes mcast: 0 pkt, 0 bytes
     2271895 packets input, 639427117 bytes, 0 no buffer
     Received 1386034 broadcasts (89547 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     417206 packets output, 35944753 bytes, 0 underruns
     0 output errors, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out

Everyone's tags (3)
3 REPLIES 3
Beginner

How many broadcasts are too many broadcasts.

Where are you seeing the drops?

Beginner

How many broadcasts are too many broadcasts.

Hi Benjamin,

here is the number of drops and flushes since I cleared the counters.

Input queue: 0/4096/917/917 (size/max/drops/flushes); Total output drops: 0

Contributor

How many broadcasts are too many broadcasts.

I've seen 16 broadcast packets per second in a big VLAN without any problems.  You should assess the quantity based on the number of hosts in the VLAN.   Perform a packet capture and you can analyze the top broadcasters in Wireshark.

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