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C
ONFIGURING
THE
S
WITCH
3-64
CLI – This example enables SSH, sets the authentication parameters, and
displays the current configuration. It shows that the administrator has
made a connection via SHH, and then disables this connection.
Configuring Port Security
Port security is a feature that allows you to configure a switch port with
one or more device MAC addresses that are authorized to access the
network through that port.
When port security is enabled on a port, the switch stops learning new
MAC addresses on the specified port when it has reached a configured
maximum number. Only incoming traffic with source addresses already
stored in the dynamic or static address table will be accepted as authorized
to access the network through that port. If a device with an unauthorized
MAC address attempts to use the switch port, the intrusion will be
detected and the switch can automatically take action by disabling the port
and sending a trap message.
To use port security, specify a maximum number of addresses to allow on
the port and then let the switch dynamically learn the <source MAC
address, VLAN> pair for frames received on the port. Note that you can
also manually add secure addresses to the port using the Static Address
Table (page 3-121). When the port has reached the maximum number of
MAC addresses the selected port will stop learning. The MAC addresses
Console(config)#ip ssh server 4-49
Console(config)#ip ssh timeout 100 4-50
Console(config)#ip ssh authentication-retries 5 4-51
Console(config)#ip ssh server-key size 512 4-51
Console(config)#end
Console#show ip ssh 4-55
SSH Enabled - version 2.0
Negotiation timeout: 120 secs; Authentication retries: 5
Server key size: 512 bits
Console#show ssh 4-55
Connection Version State Username Encryption
0 2.0 Session-Started admin ctos aes128-cbc-hmac-md5
stoc aes128-cbc-hmac-md5
Console#disconnect 0 4-25
Console#