Six examples of network trouble shooting

Our local area network is a UNIX communication server and multiple win 95 workstations connected through the hub, using the bay router and modem through the X.25 to connect with the superior line, commonly used in IE 4.0 Outlook to send and receive mail.

Failure one: The local server address is 162.131.1.1, after installing UNIX, TCP/IP and 3c509 network card, the server and Nic do not pass.

As a result of the failure in the installation process, first check TCP/IP and network adapter configuration, with #netconfig reconfiguration, pay attention to host network address and subnet mask is correct, be sure to correct, then ping 162.131.1.1 display:

Ping SendTo cant Assign requested address

Ping wrote 162.131.1.1 64chars,ret=-1

4 packets transmitted, 0 packets received,100% packet loss

Description The server can send packets, but did not receive the card receipt packet, the server and network card link. Software configuration is no problem, can only find the reason from the NIC, the NIC is inserted tightly, but the network card is not bright, it is estimated that the NIC is bad, with the same model 3c509 card replacement, after the boot ping 162.131.1.1, show: bytes from the 162.131.1.1 ttl=255 time =0ms. Failure elimination.

Fault two: Not connected to the other remote server 162.18.1.1.

Ping 162.18.1.1 First display:

Packets transmitted, 0 packets received,100% packet loss (no pass)

From the local server to the other server experienced eight links, namely the local server, Hub, router, modem on the X.25 line to each other modem, router, Hub, server, which link out of the problem. First check the local area network, found that the hub lights normal, the nodes unobstructed; then check modem and bay router, Ping 162.131.1.2 (routing address), server and router connectivity, modem CD, TD, RD, tr lights are shiny, Ping 88.109.131.1 (Wide network address), the server and X.25 network connectivity, the local network is normal. Ping 162.18.1.1, still not pass, the problem may be out of each other. Contact with the other side, the other network operation is normal. Carefully look at the configuration of the router, the other routing parameters have been added to the local routing configuration, routing configuration is not a problem. Please check the routing situation, the other side in the routing firewall will our routing table parameters shielding, the routing table parameters Jie Shi, a ping on the pass, the failure to eliminate.

Failure 3:1 account for "Keji" users into the e-mail system, when sending mail, stop in the "connected, please wait" window, unable to send and receive e-mail.

Due to the failure of the incoming and outgoing messages, Detailed view error message:

Error processing required task: Unable to find host MAIL.JINGSHAN.JINGMEN.HUBEI.PBC.CNFN, please check that the server name, account "Keji protocol SMTP, port 25, secure SSL" is entered correctly, and therefore suspect that the e-mail system is having problems. Check the TCP/IP configuration and messaging system DNS configuration as normal. Check wiring, no abnormalities found. Then you have to find the reason on the server. Related to host information configuration are:

/etc/named.boot,dns Startup configuration file

/var/named/local.zone, configuring host name to IP information

/var/named/local.rev, configuring reflexive information for IP to host

/var/named/localhost.rev, define Lookback address information

/etc/resolv.conf, define the host address and domain name resolution address.

Open the configuration one by one and find/etc/resolv.conf empty and join:

NameServer 162.131.1.1 (server address)

Domain JINGSHAN.JINGMEN.HUBEI.PBC.

CNFN (host domain name)

In/USR/LIB/SENDMAL.CF (SMTP configuration file), add:

DDjingshan.jingmen.hubei.pbc.cnfn.

Reboot the machine to remove the problem.

Failure 4:1 account for "Keji" users when sending and receiving mail, "Please enter the server's username and password, username: keji Password: * * * * * * *, the user entered the user name and password, still stopped on the window, can not send mail."

In the determination of network cable connectivity and Outlook system configuration is correct, the fault must be on the server, there are two possible: first, opened the Keji account did not; the other is opened the account, the password and the user password is the same. After checking: In the server,/usr/spool/mail no Keji account, with #scoadmin to establish Keji, and make the key and user key, the fault immediately eliminate.

A user with the fault 5:1 account "Keji" can only send messages when they use Outlook to send and receive messages, but they do not receive messages.

Click "Send Receive" appear "Cannot connect server, account: Keji, Protocol POP3" information prompt. There may be a problem with the server POP3 installation. Impact POP3 Normal work has three files:/etc/popper, etc/services,/ETC/INETD.CF, where/etc/popper is an executable file, to release its permissions. Properly configure other two file content, use Netstat-a lookup .pop, started, but still can't receive mail, view/usr/spool/mail directory Keji permissions are: rw---, chmod 777 Keji to open their permissions, received mail success.

Fault Six: The user Keji with Outlook to send and receive mail, only receive the message, cannot send out the mail.

Able to receive mail instructions there is no problem with the wiring and user configuration. The reason is on the server. View error message: "Unable to connect to server, account: Keji, protocol SMTP, etc." has two files that affect SMTP:/usr/lib/sendmail Execute file and configuration file/USR/LIB/SENDMAIL.CF. First let loose the SendMail permission, will sendmail.cf the correct change, restarts the server, sends the mail to be successful.