Troubleshooting and resolving the high latency problem of SSH Telnet Server in an enterprise Linux

First,description of problem phenomena

After successful installation of a Dell Server Rhel 6.8 System, the user reflects a high latency when logging in to the server via SSH, and can delay up to 6-7s or even direct error.

Connecting to 10.0.0.10:22 ...

Connection established.

To escape to local shell, press ' ctrl+alt+] '.

Information to display when connecting

Last Login:thu Jul 7 16:24:56 from 10.0.0.10

Wait a long time before showing successful connection

Second,Problem Analysis

2.1 Collecting information

After checking, the interface state of the server network port and the uplink switch is normal, the physical link is not faulty, and the result of ping the server from other devices is normal. It is also found that the SSH function of other servers in the same environment is normal and the problem cannot be resolved by executing the command sshd Restart to restart the SSH service.

2.2 Fault Diagnosis

This problem arises because SSH when there's a connection coming up. DNS Parse, if you configure the wrong DNS server, or DNS parsing takes too much time to cause a longer pause

Third,Problem Handling

, Workaround:

1. Check if an error is configured of DNS, If you have to remove it first;

through vi/etc/sysconfig/network-scripts/ifcfg-em0 command to enter the NIC em0 the configuration file that will take DSN after the content is deleted, and then run the command to restart the network connection, Service Network Restart

2. To change the value of the configuration item Usedns to No, the steps are:

Execute command: Vim/etc/ssh/sshd_config

the first 5 the comment of the line is removed and the value is changed to No

#Compression delayed

#ClientAliveInterval 0

#ClientAliveCountMax 3

#ShowPatchLevel No

Usedns No

#PidFile/var/run/sshd.pid

#MaxStartups 10

#PermitTunnel No

#ChrootDirectory None

Change the value of Usedns to No

Then execute the command: sshd restart, restart the SSH service, and then run the service network restart to restart the network connection.

Four,Results Feedback

Through the above two methods, the customer again by remote login to the server no longer a high latency or logon failure situation, the problem is resolved.

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Troubleshooting and resolving the high latency problem of SSH Telnet Server in an enterprise Linux