No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

FAQ-What Do the States Displayed with the display tcp status Command Mean

Publication Date:  2012-07-27 Views:  31 Downloads:  0
Issue Description
Q:
What do the states displayed with the display tcp status command mean?
<NE40>dis tcp status
TCPCB     Tid/Soid    Local Add:port     Foreign Add:port     VPNID State
0c7c6564   79 /1    0.0.0.0:21               0.0.0.0:0                14849 Listening
0bf5a7e4   49 /1     0.0.0.0:23               0.0.0.0:0                14849 Listening
0c80e504  49 /3     19.30.0.202:23     19.30.0.250:4390    0     Established
0b1c57e4  49 /4     19.30.0.202:23     19.60.3.88:3617      0     Established 
 
Alarm Information
Null
Handling Process
A:
This command is generally used to locate problems related to TCP, especially the disconnection of BGP, LDP, FTP, or Telnet sessions. For all upper-layer protocols using TCP as the transmission protocol, we can use this command to immediately learn the current TCP status. Before viewing the TCP status, we need to know the roles of both ends, that is, which is the client and which is the server, between which the TCP connection is set up. Generally, the port of the server has the well-known port number, such as 179 for the BGP server, 646 for the LDP server, 21/20 for the FTP server, and 23 for the Telnet server.
From the preceding information, we can find four TCP connections exist currently, including three Telnet connections and one FTP connection. In addition, the local device at 19.30.0.202 serves as the server.
Note: What we need to learn is the TCP states, which are divided into the following:
Listening: Indicates that the server is in the listening state, that is, the initial TCP state. At this time, the TCP server only monitors the port.
syn_sent: Indicates that the client initiates the first handshake, that is, the first SYN packet.
syn_rcvd: Indicates that the server receives the first handshake, that is, the SYN packet received by the server from the client.
Established: Indicates that the TCP connection is established.
fin_wait_1: Indicates that the device initiatively shutting down the TCP connection sends the FIN packet to the peer device.
Fin_wait_2: Indicates that the device initiatively shutting down the TCP connection sends the FIN packet and receives the FIN packet from the peer device.
time_wait: Indicates that the device initiatively shutting down the TCP connection receives the FIN and ACK packets from the other device.
close_wait: Indicates that the device passively shutting down the TCP connection receives the FIN packet from the device initiatively shutting down the TCP connection. 
 
Root Cause
Null
Suggestions
Null

END