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Network tools on the Linux system very much, how to choose according to actual needs, said hand tool? In this to make a brief introduction:
Observation of network traffic:
"Sar -n DEV 1 5" can count on the network flow rate of each card:
# Sar -n DEV 2 5
...
02:47:12 PM IFACE rxpck / s txpck / s rxkB / s txkB / s rxcmp / s txcmp / s rxmcst / s
02:47:14 PM lo 0.00 0.00 0.00 0.00 0.00 0.00 0.00
02:47:14 PM eth0 2.51 0.00 0.17 0.00 0.00 0.00 0.00
...
ptraf is a powerful tool to observe network flow, it allows you to observe the gradual deepening, from the hardware layer (NIC), the network layer (IPv4, IPv6), to the transport layer (TCP, UDP etc.), until each pair socket pair.
iptraf-d
Observe the state of the network connection:
"Netstat -a"
This is the traditional tool, but it can not handle the massive network connection. So on a host of large-scale network connection, it is recommended to use ss.
# netstat -a
Active Internet connections (servers andestablished)
Proto Recv-QSend-QLocal Address Foreign Address State
tcp 0 0 *: mysql *: * LISTEN
tcp 0 0 *: 5901 *: * LISTEN
...
tcp 0 104bj71s060.chn.hp.com:ssh 16.169.16.67:52681 ESTABLISHED
"Ss -a" lists all network connections. ss particularly suitable host massive connection.
If you add "-p" option, you can display the corresponding process ID.
# Ss -a
State Recv-QSend-Q Local Address: Port Peer Address: Port
LISTEN 0 50 *: mysql *: *
LISTEN 0 5 *: 5901 *: *
...
LISTEN 0 128 ::: 38246 ::: *
ESTAB 0 184 16.187.252.58:ssh 16.169.16.67:52681
Observation of static statistics:
"Netstat -i"
# Netstat -i
Kernel Interfacetable
Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1500 0572421962 0 0 016831237 0 0 0BMRU
lo 16436 0 556534 0 0 0 556534 0 0 0LRU
ifconfig can see a small card-level statistics, packet number, collision, errors and so on:
# Ifconfig eth0
eth0 Link encap: Ethernet HWaddr00: 19: BB: 5B: 07: 34
inet addr: 16.187.252.58 Bcast: 16.187.255.255 Mask: 255.255.252.0
inet6 addr: fe80 :: 219: bbff: fe5b: 734 / 64Scope: Link
UP BROADCAST RUNNING MULTICAST MTU: 1500 Metric: 1
RX packets: 572422657errors: 0dropped: 0overruns: 0frame: 0
TX packets: 16831252errors: 0dropped: 0overruns: 0carrier: 0
collisions: 0txqueuelen: 1000
RX bytes: 50512945748 (47.0GiB) TX bytes: 11194760435 (10.4GiB)
Interrupt: 19Memory: f0500000-f0520000
"Ip -s link" substantially similar information see:
# Ip -s link
1: lo: mtu16436qdisc noqueue state UNKNOWN
link / loopback00: 00: 00: 00: 00: 00brd00: 00: 00: 00: 00: 00
RX: bytes packets errors dropped overrun mcast
2255610398556534 0000
TX: bytes packets errors dropped carrier collsns
2255610398556534 0000
2: eth0: mtu1500qdisc pfifo_fast state UP qlen1000
link / ether00: 19: bb: 5b: 07: 34brd ff: ff: ff: ff: ff: ff
RX: bytes packets errors dropped overrun mcast
32683320875724229790 0016733497
TX: bytes packets errors dropped carrier collsns
2604833405168312850 000
"Netstat -s" provides statistical information under each protocol, some statistics such as retransmit is useful only "netstat -s" can be seen:
# Netstat -s
...
Tcp:
71479active connections openings
7181passive connection openings
13723failed connection attempts
407connection resets received
1connections established
18969163segments received
11210435segments send out
85883segments retransmited
0bad segments received.
80162resets sent
...
475fast retransmits
30forward retransmits
110retransmits inslow start
22772other TCP timeouts
5sack retransmits failed
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