Command Authorization; Protection From Tcp Tiny And Overlapping Fragment Attacks; Enabling Scp And Ssh - Dell C9000 Series Networking Configuration Manual

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Command Authorization

The AAA command authorization feature configures the system 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: %SYSTEM-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.

Secure shell (SSH) is a protocol for secure remote login and other secure network services over an insecure

network. The Dell Neetworking OS is compatible with SSH versions 1.5 and 2, both the client and server

modes. SSH sessions are encrypted and use authentication.

For details about the command syntax, refer to the Security chapter in the Dell Networking OS Command

Line Interface Reference Guide.

SCP is a remote file copy program that works with SSH and is supported on the switch.

The Windows-based WinSCP client software is not supported for secure copying between a PC

and a Dell 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 specifying the host name, username, port number, and version of the SSH

EXEC Privilege mode

ssh {hostname} [-l username | -p port-number | -v {1 | 2}