Port Security
Switches learn MAC addresses as frames are forwarded through switch ports. Port security allows you to limit the number of MAC addresses that can be learned on a port, configure static MAC addresses, and set penalties if that port is used by unauthorized users. Users can restrict, shutdown, or protect port security commands.
| Command | Description |
|---|---|
| (config-if)# switchport mode {access, trunk} | Null |
| (config-if)# [no] switchport port-security | To disable port-security |
| (config-if)# switchport port-security maximum 1 | Max no. of allowed MACs. |
| (config-if)# switchport port-security mac-address 1234.5678.9abc | To allow a MAC on this port. |
| (config-if)# switchport port-security mac-address sticky | To allow learning of connected macs until MAC Address reached. |
| (config-if)# switchport port-security violation shutdown | To shutdown port when other device gets connected. |
| (config-if)# shutdown (config-if)# no shutdown | enable again if after port-security violation. |
| (config)# errdisable recovery cause psecure-violation | enable again if automatically after problem is fixed. |
| (config)# errdisable recovery interval 42 | Recheck every 42 seconds. |
Port-Security Terms of Violation:
Troubleshooting Port Security:
| Command | Description |
|---|---|
| # show port-security [interface g1/1] | port status, violation mode, max/total MACs,… |
| # show port-security address | Secure MACs on ports. |
| # show errdisable recovery | Check if auto recovery is enabled. Disabled by default. |
CCNA Cheatsheet
A CCNA certification proves you have the competencies needed to navigate an ever-changing IT landscape. CCNA exams cover network fundamentals, IP services, security fundamentals, automation, and programmability. Designed for agility and versatility, CCNA proves you have the skills needed to manage and optimize today’s most advanced networks. CCNA training courses and exams are the foundation for advancing your career in any direction. A Cisco certification is living proof of the standards and rigor your organization recognizes and trusts to meet and exceed market demands. Here is a cheat sheet for CCNA Examination.