You might argue that the wall jack has no connection to a switch, but couldn't someone just pull the Ethernet cable from a working PC and connect to the network that way? You might think this an unlikely scenario, but it does happen. At my organization, we had salesmen coming in to demo products, and they would just pull the Ethernet jack off a PC and connect it to their laptop, hoping to get Internet access.
The idea that anyone could just come in and access our network scared me — and the possibility should scare you too.follow link
Limit ports access for particular MAC a - Cisco Community
What frightened me the most were the various viruses or worms that their PCs might contain. Remember, not everyone recognizes the importance of effective security measures, and you don't want to trust your network's security to their apathy. I turned to switch port security to help solve the problem. Let's look at how you can use Cisco's Port Security feature to protect your organization. In its most basic form, the Port Security feature remembers the Ethernet MAC address connected to the switch port and allows only that MAC address to communicate on that port.
If any other MAC address tries to communicate through the port, port security will disable the port. Most of the time, network administrators configure the switch to send a SNMP trap to their network monitoring solution that the port's disabled for security reasons. Of course, implementing any security solution always involves a trade-off — most often, you trade increased security for less convenience.
Restrictions for Port Security
When using port security, you can prevent devices from accessing the network, which increases security. However, as you know, there's usually a downside. In this case, it's that the network administrator is the only one who can "unlock" the port, which can cause problems when there are legitimate reasons to change out devices. By entering the most basic command to configure port security, we accepted the default settings of only allowing one MAC address, determining that MAC address from the first device that communicates on this switch port, and shutting down that switch port if another MAC address attempts to communicate via the port.
But you don't have to accept the defaults. As you can see in the example, there are a number of other port security commands that you can configure. Here are some of your options:. However, you need to be very careful with this option if you enter this command on an uplink port that goes to more than one device. As soon as the second device sends a packet, the entire port will shut down. Sets the interface mode as access; an interface in the default mode dynamic desirable cannot be configured as a secure port.
Optional Sets the maximum number of secure MAC addresses for the interface. The range is 1 to ; the default is 1.
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Optional Sets the violation mode, the action to be taken when a security violation is detected, as one of these:. Note When a secure port is in the error-disabled state, you can bring it out of this state by entering the errdisable recovery cause psecure-violation global configuration command or you can manually reenable it by entering the shutdown and no shut down interface configuration commands. Optional Enters a secure MAC address for the interface.
Cisco CCNA – Port Security and Configuration
You can use this command to enter the maximum number of secure MAC addresses. The interface converts the sticky secure MAC addresses to dynamic secure addresses. To delete all the sticky addresses on an interface or a VLAN, use the no switchport port-security sticky interface interface-id command.
The address keyword enables you to clear a secure MAC addresses. The interface keyword enables you to clear all secure addresses on an interface.
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This example shows how to enable port security on Fast Ethernet port 12 and how to set the maximum number of secure addresses to 5. The violation mode is the default, and no secure MAC addresses are configured. You can use port security aging to set the aging time and aging type for all secure addresses on a port. Use this feature to remove and add PCs on a secure port without manually deleting the existing secure MAC addresses while still limiting the number of secure addresses on a port.
Enters interface configuration mode for the port on which you want to enable port security aging. The static keyword enables aging for statically configured secure addresses on this port. If the time is equal to 0, aging is disabled for this port. The type keyword sets the aging type as absolute or inactive. For absolute aging, all the secure addresses on this port ago out exactly after the time minutes specified and are removed from the secure address list.
For inactive aging, the secure addresses on this port ago out only if there is no data traffic from the secure source address for the specified time period. To disable port security aging for all secure addresses on a port, use the no switchport port-security aging time interface configuration command. Use the show port-security command to display port-security settings for an interface or for the switch.
Catalyst 4500 Series Switch Cisco IOS Software Configuration Guide, 12.2(25)EW
Displays port security settings for the switch or for the specified interface, including the maximum allowed number of secure MAC addresses for each interface, the number of secure MAC addresses on the interface, the number of security violations that have occurred, and the violation mode. Displays all secure MAC addresses configured on all switch interfaces or on a specified interface with aging information for each address.
This example displays output from the show port-security command when you do not enter an interface:. This example displays output from the show port-security command for a specified interface:. Skip to content Skip to footer. Book Contents Book Contents.
Find Matches in This Book. PDF - Complete Book 6. February 13, Configuring Port Security. This chapter consists of these sections: After you have set the maximum number of secure MAC addresses on a port, the secure addresses are included in an address table in one of these ways: You can configure the interface for one of these violation modes, based on the action to be taken if a violation occurs: Configuring Port Security These sections describe how to configure port security: Switch configure terminal Enter configuration commands, one per line.
Enabled Port Status: Secure-up Violation Mode: Shutdown Aging Time: Absolute SecureStatic Address Aging: To configure port security aging, perform this task: