Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.112.1P1 - Page 786

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 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 hostname, username, port number,encryption cipher,HMAC algorithm and version of the SSH client. EXEC Privilege mode ssh {hostname} [-l username | -p port-number | -v {1 | 2}| -c encryption cipher | -m HMAC algorithm 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). • SSH V2 is enabled by default on all the modes. • Display SSH connection information. EXEC Privilege mode show ip ssh Specifying an SSH Version The following example uses the ip ssh server version 2 command to enable SSH version 2 and the show ip ssh command to confirm the setting. Dell(conf)#ip ssh server version 2 Dell(conf)#do show ip ssh SSH server : enabled. SSH server version : v2. SSH server vrf : default. SSH server ciphers : 3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192- ctr,aes256-ctr. SSH server macs : hmac-md5,hmac-md5-96,hmac-sha1,hmac-sha1-96,hmac-sha2-256,hmac- sha2-256-96. SSH server kex algorithms : diffie-hellman-group-exchange-sha1,diffie-hellman-group1- sha1,diffie-hellman-group14-sha1. Password Authentication : enabled. Hostbased Authentication : disabled. RSA Authentication : disabled. Vty Encryption HMAC Remote IP Dell(conf)# 786 Security