Broadcast Suppression Configuration Guidelines And Restrictions - Cisco 7609 Configuration Manual

Broadcast Suppression Configuration Guidelines and Restrictions

Figure 29-1 Broadcast Suppression
Total
number of
broadcast
packets
or bytes
The broadcast suppression threshold numbers and the time interval combination make the broadcast
suppression algorithm work with different levels of granularity. A higher threshold allows more
broadcast packets to pass through.
Broadcast suppression on the Cisco 7600 series routers is implemented in hardware. The suppression
circuitry monitors packets passing from a LAN interface to the switching bus. Using the
Individual/Group bit in the packet destination address, the broadcast suppression circuitry determines if
the packet is unicast or broadcast, keeps track of the current count of broadcasts within the 1-second
interval, and when a threshold is reached, filters out subsequent broadcast packets.
Because hardware broadcast suppression uses a bandwidth-based method to measure broadcast activity,
the most significant implementation factor is setting the percentage of total available bandwidth that can
be used by broadcast traffic. Because packets do not arrive at uniform intervals, the 1-second interval
during which broadcast activity is measured can affect the behavior of broadcast suppression.
Note Multicast traffic cannot be suppressed.
Broadcast Suppression Configuration Guidelines and
Restrictions
Follow these guidelines and restrictions when configuring broadcast suppression:
•
•
•
•
•
•
Note With Release 12.1(11b)E and later, when you are in configuration mode you can enter EXEC mode-level
commands by entering the do keyword before the EXEC mode-level command.
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
29-2
0 T1 T2
Broadcast suppression is supported on Layer 2 and Layer 3 LAN interfaces.
Broadcast suppression is not supported on VLAN interfaces.
You can specify broadcast suppression in hundredths of a percent.
A threshold value of 0 suppresses all broadcast traffic.
A threshold value of 100 percent does not suppress any broadcast traffic.
The broadcast suppression configuration is cleared if you change the configuration of a LAN
interface from Layer 3 to Layer 2 or from Layer 2 to Layer 3.
Threshold
T3 T4 T5 Time
Chapter 29 Configuring Broadcast Suppression
78-14064-04