I recently started reevaluating how we do port security as a result of a recent customer's information security audit. We normally turn on port security and set the maximum MAC addresses to 1 (the default) or 2 (if there is an IP phone connected). The default behavior is to disable the port when the MAC changes or if the number of concurrent MAC’s exceeds the maximum.
- One Switch For Mac
- Cisco Switch Mac Address
- Show Mac Address Table Cisco Switch
- Switch Mac Address Table
- Ethernet Switch Mac Address
My switch's arp cache ('show arp') has only 7 entries, while its mac address table ('show mac-address') has over 200 entries. The best way to get the data you're looking for is to use nmap or similar to do a ping scan and check the arp cache afterwards. Yes, all switches have a MAC address. How this MAC address is implemented depends on the vendor. Some switches have the same MAC address on all ports. Cisco switches have a different MAC address on each port and one main MAC address that refers to the switch itself. These MAC addresses are only used for traffic that is destined to or generated.
In Extreme devices, the individual ports do not have a specific hardware address/mac address. Only the switch mac address is used for communicating with other devices. Use the command, 'show switch' to know the mac-address of the switch.
One Switch For Mac
However during testing I discovered this didn’t work exactly like I expected. Port security was enforced as long as a device stayed connected to the port. If the port was disconnected, the switch would remove the pre-existing MAC’s and ANY new device could connect, as long as the maximum was not exceeded. While this prevents unauthorized hubs and switches, it doesn’t prevent someone from unplugging a device and plugging in a different unauthorized device.
Cisco Switch Mac Address
The solution to this is to use the sticky option on the port security interface command: [more]
- switchport port-security – enables port security, optional “maximum <n>” to set the max greater than 1
- switchport port-security mac-address sticky – turns on the sticky MAC feature
After enabling, you will notice the currently connected MAC address(es) will appear in the running config:
- switchport port-security
- switchport port-security mac-address sticky 0080.6433.xxxx
This will stay in the config until the switch is rebooted, so it’s important to write the config.
Application blocked by java security for mac. Other related commands:
- show port-security address – lists all the learned MAC addresses by interface
- show port-security interface fa0/1 – shows the detailed port security settings for an interface, including enable/disable status
- clear port-security sticky interface fa0/1 – clears the learned sticky MAC addresses, must be done prior to a shut/no shut to re-enable a port disabled due to port security
When you use sticky MAC addresses you'll want to make sure that the MAC addresses are cleared off of a switch when a device is moved. We had a laptop that was moved from one client location to another and one of the distribution switches was thinking the device was plugged into the old switch and the other distribution switch thought it was plugged ito the new switch. This created a situation where some network traffic was reaching the laptop and some was going into a black hole. After clearing the the sticky MAC addresses on the old switch the problem was resolved.
Update: You might also be interested in a couple stick MAC address tips.
You can also enter a MAC address manually into the table. These static entries are retained even after the switch is rebooted. To better understand how switches learn MAC addresses, consider the following example: When SW1 is first powered on, the MAC address table will be empty: ![Mac Address For Switch Ports Mac Address For Switch Ports](/uploads/1/1/8/6/118659688/921045377.jpg)
But, when Host A sends a frame to Host B, the switch will add the HostA’s MAC address to its MAC address table, associating it with the interface Fa0/1. The switch will also learn the Host B’s MAC address when Host B responds to Host A and associate it with its interface Fa0/2: Layer 2 switching How switches forward frames
Show Mac Address Table Cisco Switch
Switch Mac Address Table
![Mac Address For Switch Ports Mac Address For Switch Ports](/uploads/1/1/8/6/118659688/921045377.jpg)