Using Passwords, Port Security, and Authorized IP Managers To Protect Against Unauthorized Access Configuring and Monitoring Port Security

Physical Topology

Logical Topology for Access to Switch A

Switch A

Port Security Configured

Switch B

MAC Address Authorized by Switch A

Switch C

MAC Address NOT Authorized by Switch A

PC 1

MAC Address Authorized by Switch A

PC 2

MAC Address NOT Authorized by Switch A

PC 3

MAC Address NOT Authorized by Switch A

Switch A

 

Port Security

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Configured

 

 

 

 

 

 

PC 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MAC Address

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Authorized by Switch A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch B

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MAC Address

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Authorized by

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PC1 can access Switch A.

PCs 2 and 3 can access Switch B and Switch C, but are blocked from accessing switch A by the port security settings in switch A.

Switch C is not authorized to access Switch A.

Security,

Using

 

Figure 7-3. Example of How Port Security Controls Access

 

 

N o t e

Broadcast and Multicast traffic is not “unauthorized” traffic, and can be read

 

by intruders connected to a port on which you have configured port security.

 

 

Trunk Group Exclusion

Port security does not operate on either a static or dynamic trunk group. If you configure port security on one or more ports that are later added to a trunk group, the switch will reset the port security parameters for those ports to the factory-default configuration. (Ports configured for either Active or Passive LACP, and which are not members of a trunk, can be configured for port security.)

Planning Port Security

1.Plan your port security configuration and monitoring according to the following:

a. On which ports do you want to configure port security?

Authorized and

Port Passwords,

IP

 

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