D-ITG seems to be much powerful and efficient than iperf

Official website: http://www.grid.unina.it/software/ITG/
It can provide much more bandwidth without consuming much CPU. Here is simple example.
Receiver:

./ITGRecv

Sender:

ITGSend -a  -sp 9400 -rp 9500 -C 100 -c 1000 -t 30000 -x log.txt 

This will use UDP source port 9400, dst port 9500, send 100pps each 1000bytes long during 30000ms. After testing it will create log file log.txt on the receiver side.
Analyze logs:

./ITGDec log.txt

iperf multicast

Как оказалось, iperf умеет работать с мультикаст пакетами.
На сервере(принимает мультикаст): iperf -s -u -B 239.195.0.199 -i 1 -p1234
На клиенте(отправляем мультикаст): iperf -c 239.195.0.199 -u -T 32 -i 1 -p 1234 -b 4M -t 60
Отсюда: http://taosecurity.blogspot.com/2006/09/generating-multicast-traffic.html