Failed to telnet to s series switch

1

For S series switches (except S1700 switches), if you fail to log in to the Telnet server through Telnet, troubleshoot the failure as follows:
1. Check whether the number of login users reaches the upper limit.
Log in to the switch through the console port, and run the display users command to check whether all VTY user interfaces are in use. By default, the maximum number of VTY user interfaces is 5. You can run the display user-interface maximum-vty command to check the maximum number of login users allowed by a switch.

2. Check whether an ACL is configured in the VTY user interface view. (Telnet IPv4 is used as an example.)
Run the user-interface vty command on the Telnet server to enter the user interface view. Then run the display this command to check whether an ACL is configured in the VTY user interface view. If so, record the ACL number.
Run the display acl acl-number command on the Telnet server to check whether the IP address of the Telnet client is denied in the ACL. If so, run the undo rule rule-id command in the ACL view to delete the deny rule, then run the related command to permit the IP address of the client in the ACL.

3. Check whether the access protocol is correctly configured in the VTY user interface view.
Note that by default, the switch uses Telnet in V200R006 and earlier versions, so you do not need to configure protocol inbound telnet; the switch uses SSH in V200R007 and later versions, so you must configure protocol inbound telnet if you want to log in through Telnet.
Run the user-interface vty command on the Telnet server to enter the user interface view and then run the display this command to check whether protocol inbound is set to telnet or all. (By default, the system supports the SSH protocol.) If protocol inbound is not set to telnet or all, run the protocol inbound { telnet | all } command to allow Telnet users to connect to the switch.

4. Check whether an authentication mode is set for login users in the user interface view.
- If password authentication is configured using the authentication-mode password command, you must enter the password upon login.
- If AAA authentication is configured using the authentication-mode aaa command, you must run the local-user command to create a local AAA user.

Other related questions:
DHCP configuration on S series switch does not take effect
DHCP configuration may not take effect on an S series switch due to the following reasons: 1. DHCP server is disabled on the switch. 2. The DHCP address pool is configured incorrectly. 3. No IP network segment is specified on the interface connected to DHCP clients, or the specified IP network segment is on a different network segment from the address pool. 4. If ACL resources are exhausted, the DHCP commands run globally or on an interface will not take effect.

What should I do if the configuration of an S series switch is lost after restart
If the configuration of an S series switch (except the S1700) is lost after restart, the possible reasons are as follows: the configuration fails to be saved or the specified startup file is incorrect. Handle the problem as follows:
1. If the configuration fails to be saved, run the following command to save the configuration:
<HUAWEI> save
The current configuration will be written to the device. Are you sure to continue?[Y/N]Y
Info: Please input the file name(*.cfg,*.zip)[vrpcfg.zip]:Y
When the configuration of a new switch is saved for the first time, the system asks you to enter the name of the configuration file to which the configuration is to be saved, which is vrpcfg.zip by default or a created file with name extension .zip or .cfg. If the configuration does not need to be saved to other files separately, press Enter. (Press Enter or enter the new configuration file name. Otherwise, the configuration cannot be written to the configuration file and the switch still restarts with no configuration.)
If the message Info: Save the configuration successfully. is displayed, the configuration is saved successfully. You are advised to run the display saved-configuration command to verify that the configuration is successfully written to the configuration file.
2. If the configuration file for the next startup is not specified or the name of the specified file is different from that of the saved configuration file, perform the following operations:
a. Check the configuration file.
<HUAWEI> dir /all
b. Check whether the name of the configuration file for the next startup (represented by the Next startup saved-configuration file field) is the same as that of the saved configuration file. If the field is empty or specifies another file name, run a command to specify the saved configuration file for the next startup.
<HUAWEI> display startup
c. Specify the configuration for the next startup. startup saved-configuration vrpcfg.zip
3. If DHCP-related configurations are lost after DHCP is configured and saved on a new switch that is started for the first time, the possible cause is as follows:
If a switch starts without any configuration, the switch automatically starts the auto-config process. This process triggers the DHCP function for the switch to automatically obtain an IP address and the configuration file from a DHCP on the network. When DHCP is manually configured, the auto-config process is automatically disabled, so the DHCP function is also automatically disabled. Therefore, DHCP-related commands are lost after the DHCP configuration is saved.

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