shows how data flows when the network is configured for UDP flooding.
Figure 19-3: Data flow with UDP flooding and IRDP.
Note This topology is broadcast intensive—broadcasts sometimes consume 20 percent of the Ethernet bandwidth. However, this is a favorable percentage when compared to the configuration of IP helper addressing, which, in the same network, causes broadcasts to consume up to 50 percent of the Ethernet bandwidth.
If the hosts on the trader networks do not support IRDP, the Hot Standby Routing Protocol (HSRP) can be used to select which router will handle unicast traffic. HSRP allows the standby router to take over quickly if the primary router becomes unavailable. For information about configuring HSRP, see "Using HSRP for Fault-Tolerant IP Routing."
By default, the router performs UDP flooding by process switching the UDP packets. To increase performance on AGS+ and Cisco 7000 series routers, enable fast switching of UDP packets by using the following command:
ip forward-protocol turbo-flood
Note Turbo flooding increases the amount of processing that is done at interrupt level, which increases the CPU load on the router. Turbo flooding may not be appropriate on routers that are already under high CPU load or that must also perform other CPU-intensive activities.
