D-Link DGS-3208TG User Guide - Page 36

Gigabit Ethernet Switch User's Guide domains are implemented at each switch port, they can be quite effective in limiting the scope of broadcast storms. Eliminating Broadcast Storms SNMP agents can be programmed to monitor the number of broadcast packets on switch ports and act on the data. When the number of broadcast packets on a given port rise past an assigned threshold, an action can be triggered. When enabled, the usual action is to block the port to broadcast frames, which discards all broadcast frames arriving at the port from the attached segment. Not only does this isolate the broadcast domain, but it actually starts removing broadcast packets from the affected segment. When the number of broadcast packets falls to an acceptable level (below a falling threshold), the SNMP agent can remove the blocking condition, returning the port to its normal operational state. In the Switch, the default rising threshold is met when more than 500 broadcast packets per second are being detected on a specified port. Once the rising threshold is surpassed for a duration of more than 5 seconds, it will trigger the broadcast storm rising action configured by the user. The default falling threshold is met if there are less than 250 broadcast packets per second. It is triggered once the duration is at least 30 seconds. The actions can easily be defined by using a normal SNMP management program or through the console interface. 24