Traffic Monitoring Tool in linux

Iptraf easy to use yum install iptraf
Iptraf is an ncurses-based ip lan monitor that generates varous network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet, load info, node stats, IP checksum errors, and others. if the command is issued without any command-line options, the program comes up in interactive mode, with the varous facilities accessed through the main menu.

Nload is not simple and intuitive
Wget http://www.roland-riegel.de/nload/nload-0.7.2.tar.gz
Tar zxvf nload-0.7.2.tar.gz
Cd nload-0.7.2
./Configure; make install
Use
Use nload to press Enter. You can also specify the NIC, such as nload eth1.
You can also specify K or M to display the traffic. For example, nload-u M shows the traffic in MB.
See what other parameters or options are available.
[Root @ wdlinux ~] # Nload-u K
[Root @ wdlinux ~] # Nload-h

Ifstat is not simple and intuitive
Ifstat is a little tool to report interface activity, just like iostat/vmstat do for other system statistics.
Ifstat gathers these statistics from the kernel internal counters, which is highly operating system dependent. Right now, the following systems are supported:
Linux> = 2.2.0 (through/proc/net/dev file ).
FreeBSD> = 2.2 (using the ifmib (4) interface ).
Solaris> = 5.6 (using the kstat (3 K) interface ).
IRIX and OpenBSD (using the SIOCGIFDATA ioctl ).
NetBSD and Darwin (using the route (4) sysctl interface ).
Other BSDs (using the kvm (3) interface ).
Digital Unix (OSF/1), Tru64, and Aix (using the legacy kmem interface ).
HP-UX (using the DPLI streams interface ).
Win32 native or through Cygwin (using the GetIfTable call ).
Http://gael.roualland.free.fr/ifstat/ifstat-1.1.tar.gz wget-S
Tar zxvf ifstat-1.1.tar.gz
Cd ifstat-1.1
./Configure
Make; make install
Ifstat

Iftop is not included

Wget-S 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
Use
Iftop-I eth1-B
Iftop-I eth2-B-m 30 M
Iftop-n-I eth1
Http://jiajun.iteye.com/blog/419515

Watch ifconfig
Watch more/proc/net/dev
Watch-n 1 "/sbin/ifconfig eth0 | grep bytes"
Ulimit-n

[Root @ CactiEZ ~] # Netstat-s
[Root @ CactiEZ ~] # Sar-n DEV 1
[Root @ CactiEZ ~] # Sar-n EDEV 1 2
The-n parameter is useful. It has six different switches: DEV | EDEV | NFS | NFSD | SOCK | ALL.
DEV displays network interface information, EDEV displays statistics on network errors, NFS statistics on active NFS clients, NFSD statistics on NFS servers, and SOCK displays socket information, ALL shows ALL 5 switches. They can be used independently or together.
Rxerr/s: Bad packet received per second txerr/s: Bad packet sent per second coll/s: number of conflicts per second
Rxdrop/s: number of received packets discarded per second because the buffer is full
Txdrop/s: the number of sent packets discarded per second because the buffer is full
Txcarr/s: Number of carrier errors per second during packet sending
Rxfram/s: Number of frame alignment errors of packets received per second
Rxfifo/s
Txfifo/s