Command Authorization; Protection From Tcp Tiny And Overlapping Fragment Attacks; Enabling Scp And Ssh - Dell Z9000 Configuration Manual

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.
NOTE: 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 specify the host name, username, port number, and version of the SSH
client.
EXEC Privilege mode
ssh {hostname} [-l username | -p port-number | -v {1 | 2}
hostname is the IP address or host name of the remote device. Enter an IPv4 or IPv6 address in
dotted decimal format (A.B.C.D).
• Configure the Dell Networking system as an SCP/SSH server.
CONFIGURATION mode
ip ssh server {enable | port port-number}
• Configure the Dell Networking system as an SSH server that uses only version 1 or 2.
CONFIGURATION mode
ip ssh server version {1|2}
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Security