Port path cost 100, Port priority 128
Designated root has priority 32768, address 0000.0C00.4BD0
Designated bridge has priority 32768, address 0030.8054.6C00
Designated port is Ethernet 0/12, path cost 100
Timers: message age 20, forward delay 15, hold 1
Port Ethernet 0/25 of VLAN1 is Forwarding
Port path cost 100, Port priority 128
Designated root has priority 32768, address 0000.0C00.4BD0
Designated bridge has priority 32768, address 0030.8054.6C00
Designated port is Ethernet 0/25, path cost 100
Timers: message age 20, forward delay 15, hold 1
Port FastEthernet 0/26 of VLAN1 is Blocking
Port path cost 10, Port priority 128
Designated root has priority 32768, address 0000.0C00.4BD0
Designated bridge has priority 32768, address 0030.8054.6C00
Designated port is FastEthernet 0/26, path cost 100
Timers: message age 20, forward delay 15, hold 1
Port FastEthernet 0/27 of VLAN1 is Blocking
Port path cost 10, Port priority 128
Designated root has priority 32768, address 0000.0C00.4BD0
Designated bridge has priority 32768, address 0030.8054.6C00
Designated port is FastEthernet 0/27, path cost 100
Timers: message age 20, forward delay 15, hold 1
Viewing the CAM (MAC Address) Table on a Set/Clear
Command−Based IOS

A switch uses the CAM table to make forwarding decisions on the switch. Let’s take a look at the available

command options, syntaxes, and an example of the output using the show cam command:

Catalyst5002> (enable) show cam ?
Usage: show cam [count] <dynamic|static|permanent|system> [vlan]
show cam <dynamic|static|permanent> <mod_num/port_num>
show cam <mac_addr> [vlan]
show cam agingtime
Catalyst5002> (enable) show cam dynamic 2
VLAN Dest MAC/Route Des Destination Ports or VCs
2 00−30−19−4C−80−A6 2/4
2 00−30−19−4C−80−A8 2/18
2 00−30−19−4C−80−A6 2/15
2 00−30−19−4C−80−A6 2/12
2 00−30−19−4C−80−BC 2/9
2 00−30−19−4C−80−3F 2/10
2 00−30−19−4C−80−D4 2/6
2 00−30−19−4C−80−B3 2/7
2 00−30−19−4C−80−A2 2/2
2 00−80−00−00−12−D0 2/22
2 00−30−19−4C−80−C4 2/1
2 00−30−19−4C−80−3B 2/23
Total Matching CAM Entries Displayed = 12
Viewing the CAM (MAC Address) Table on a CLI−Based IOS

On a CLI−based IOS, the show mac command is used to view the CAM table that makes forwarding

decisions for frames arriving on the switch. Let’s take a look at the output using the show mac command:

328