패키지 설치
# centos
yum install iftop

# ubuntu
apt-get install iftop

# 소스 설치
wget http://www.ex-parrot.com/pdw/iftop/download/iftop-0.17.tar.gz
tar -zxvf iftop-0.17.tar.gz
cd iftop-0.17
./configure
make
make install

# 실행
iftop
iftop -i eth0