Users Guide

Specifying a TACACS+ Server Host
To specify a TACACS+ server host and configure its communication parameters, use the following command.
• Enter the host name or IP address of the TACACS+ server host.
CONFIGURATION mode
tacacs-server host {hostname | ip-address} [port port-number] [timeout seconds] [key key]
Configure the optional communication parameters for the specific host:
○ port port-number: the range is from 0 to 65535. Enter a TCP port number. The default is 49.
○ timeout seconds: the range is from 0 to 1000. Default is 10 seconds.
○ key key: enter a string for the key. The key can be up to 42 characters long. This key must match a key configured on the
TACACS+ server host. This parameter must be the last parameter you configure.
If you do not configure these optional parameters, the default global values are applied.
To specify multiple TACACS+ server hosts, configure the tacacs-server host command multiple times. If you configure multiple
TACACS+ server hosts, Dell 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:
Dell#
Dell#
Command Authorization
The AAA command authorization feature configures Dell 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 )
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 Networking OS
is compatible with SSH versions 1.5 and 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 Networking OS Command Line Interface Reference Guide.
Dell Networking OS SCP, which is a remote file copy program that works with SSH.
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Security