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To specify multiple TACACS+ server hosts, configure the tacacs-server host command multiple times. If you configure
multiple TACACS+ server hosts, Dell EMC Networking OS attempts to connect with them in the order in which they were
configured.
To view the TACACS+ configuration, use the show running-config tacacs+ command in EXEC Privilege mode.
To delete a TACACS+ server host, use the no tacacs-server host {hostname | ip-address} command.
freebsd2# telnet 2200:2200:2200:2200:2200::2202
Trying 2200:2200:2200:2200:2200::2202...
Connected to 2200:2200:2200:2200:2200::2202.
Escape character is '^]'.
Login: admin
Password:
DellEMC#
Command Authorization
The AAA command authorization feature configures Dell EMC Networking OS to send each configuration command to a
TACACS server for authorization before it is added to the running configuration.
By default, the AAA authorization commands configure the system to check both EXEC mode and CONFIGURATION mode
commands. Use the no aaa authorization config-commands command to enable only EXEC mode command
checking.
If rejected by the AAA server, the command is not added to the running config, and a message displays:
04:07:48: %RPM0-P:CP %SEC-3-SEC_AUTHORIZATION_FAIL: Authorization failure Command
authorization failed for user (denyall) on vty0 ( 10.11.9.209 )
Certain TACACS+ servers do not authenticate the device if you use the aaa authorization commands level default
local tacacs+ command. To resolve the issue, use the aaa authorization commands level default tacacs+
local command.
Protection from TCP Tiny and Overlapping Fragment
Attacks
Tiny and overlapping fragment attack is a class of attack where configured ACL entries — denying TCP port-specific traffic —
is bypassed and traffic is sent to its destination although denied by the ACL.
RFC 1858 and 3128 proposes a countermeasure to the problem. This countermeasure is configured into the line cards and
enabled by default.
Enabling SCP and SSH
Secure shell (SSH) is a protocol for secure remote login and other secure network services over an insecure network. Dell EMC
Networking OS is compatible with SSH versions 2, in both the client and server modes. SSH sessions are encrypted and use
authentication. SSH is enabled by default.
For details about the command syntax, refer to the Security chapter in the Dell EMC Networking OS Command Line Interface
Reference Guide.
Dell EMC Networking OS SCP, which is a remote file copy program that works with SSH.
NOTE:
The Windows-based WinSCP client software is not supported for secure copying between a PC and a Dell EMC
Networking OS-based system. Unix-based SCP client software is supported.
To use the SSH client, use the following command.
● Open an SSH connection and specify the hostname, username, port number,encryption cipher,HMAC algorithm and version
of the SSH client.
EXEC Privilege mode
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Security