Broadcast in network.

[UshustechIT]

Hi,

We had one Procurve 6200yl (Layer 3) and three 4208vl (Layer 2) switches. The problem is sometimes we are experiencing broadcast storm in our network . But this is not happening frequnetly. Is there any way to find what causes this broadcast. Please help me.

Regards

Sreejith

[paulgear]

Hi Sreejith,

You need to check your spanning tree protocol configuration to make sure that it's turned on and that the expected switch (probably the 6200) is the root bridge of the tree.

Also check to make sure that you don't have any ports set to do STP BPDU filtering inappropriately.

See the manuals for full explanations of these features.

[UshustechIT]

Hi Paul,

Is it possible to eliminate broadcast by enabling STP?. I think STP is for avoiding loops and thus eliminating broadcast stom caused by network loops. Am I right?.

Regards

Sreejith

[paulgear]

Hi Sreejith,

Broadcasts and broadcast storms are not the same thing: broadcasts are normal and required for IPv4 networking; broadcast storms are bad and will stop your network from working.

You are right that STP is designed to find the loops in your network and block them, thus eliminating broadcast storms.  But you can customise how this works, and it is still possible to have broadcast storms with STP turned on if your network is not configured correctly.

[UshustechIT]

Thanks Paul :)

I think my term "broadcast storm" in thread confused you. Ok Paul Is there anyway to identify from which port broadcast packets are emerged hugely. Am sure its not a loop cuasing problem. I noticed that broadcast is causing problem in  a VLAN.  I think some application runninng on Hosts causing problem. Is there any chance ARP broadcast cause this kind of problem?.

Sorry for my english :)

Regrads

Sreejith

[paulgear · Accepted solution]

Hi Sreejith,

If you suspect broadcasts are causing a problem in your VLAN, you can check the port counters on the individual ports with 'show interfaces NUM' where NUM is the number of the port, e.g.:

hp2810# show int 35

 Status and Counters - Port Counters for port 35                      

  Name  :                                                                 
  Link Status     : Up  
  Totals (Since boot or last clear) :                                    
   Bytes Rx        : 420,155,086        Bytes Tx        : 3,121,362,889     
   Unicast Rx      : 1,017,954          Unicast Tx      : 2,404,587         
   Bcast/Mcast Rx  : 5741               Bcast/Mcast Tx  : 633,563           
  Errors (Since boot or last clear) :                                    
   FCS Rx          : 0                  Drops Rx        : 0                 
   Alignment Rx    : 0                  Collisions Tx   : 0                 
   Runts Rx        : 0                  Late Colln Tx   : 0                 
   Giants Rx       : 0                  Excessive Colln : 0                 
   Total Rx Errors : 0                  Deferred Tx     : 0                 
  Rates (5 minute weighted average) :
   Total Rx  (bps) : 622472             Total Tx  (bps) : 5002536   
   Unicast Rx (Pkts/sec) : 0            Unicast Tx (Pkts/sec) : 0         
   B/Mcast Rx (Pkts/sec) : 0            B/Mcast Tx (Pkts/sec) : 2         
   Utilization Rx  : 00.06 %            Utilization Tx  : 00.50 %

The line in bold shows broadcasts/multicasts sent or received.  Check the manuals if you want more details about the show interfaces command.

[UshustechIT]

Thank You paul :)