High broadcast / multicast from trunk port. 1

[shihlin]

I setup SPAN port in cat 6509, and use a Sniffer Pro to get traffic flow. However, the VLAN1 seems to have problem such as broadcast / multicast Storm, high octets/s and high utilization in Sniffer alert. The most of broadcast / multicast is happen in trunking (fiber port) in 802.1q to another Cat switch. My question is this type of broadcast is normal to trunk port? Also does STP multicast will increase the utilization? Will STP aging helps in multicasting issues?

Thanks,


SL

 

[johnilu]

Multicast/Broadcast traffic is normal to a trunk port. All multicast traffic will increase with increased utilization.

All the traffic on a trunked port is essentially multicast/broadcast traffic. Compare the number of overall packets to the number of unicast packets, broadcast packets, and multicast packets.

If you are not seeing a lot of error traffic specifically a lot of retransmits I would not worry about it. As always check for duplex mismatches as a way to clear up some of the problems.

 

[RookThis]

I would also remove any vlans that do not need to traverse the trunk. If this switch is in the distribution layer then you may not have a choice if you have dual switches for redundancy, but if it's a trunk to an access layer switch, then you probably don't need all the trunks. This could cut down on some of the traffic.