Information Technology Reference
In-Depth Information
Step 4
At this point, we paste the following commands from the Clipboard into the switch. These commands
show the time on the 2900XL and turn the port back on:
show clock
conf t
int f0/1
no shut
Step 5
By default, PortFast is off. You can confirm it two ways: The first way is that the
show spanning-tree
interface
command would not mention PortFast; the second way is to look at the running config, where
you would not see the
spanning-tree portfast
command under the interface.
2900XL#
show spanning-tree interface fastEthernet 0/1
Interface Fa0/1 (port 13) in Spanning tree 1 is FORWARDING
Port path cost 19, Port priority 128
Designated root has priority 8192, address 0010.0db1.7800
Designated bridge has priority 32768, address 0050.8039.ec40
Designated port is 13, path cost 19
Timers: message age 0, forward delay 0, hold 0
BPDU: sent 887, received 1
[Note: there is no message about being in portfast mode is in this spot...]
2900XL#
show running-config
Building configuration...
...
!
interface FastEthernet0/1
[Note: there is no spanning-tree portfast command under this interface...]
!
...
Step 6
Here is the first timing test with PortFast off:
2900XL#
show clock
*00:27:27.632 UTC Mon Mar 1 1993
2900XL#
conf t
Enter configuration commands, one per line. End with CNTL/Z.
2900XL(config)#
int f0/1
2900XL(config-if)#
no shut
2900XL(config-if)#
00:
27:27
: ST: FastEthernet0/1 -
listening
00:
27:27
: %LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up
00:
27:28
: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed
state to up
00:
27:42
: ST: FastEthernet0/1 -
learning
00:
27:57
: ST: sent Topology Change Notice on FastEthernet0/6
00:
27:57
: ST: FastEthernet0/1 -
forwarding
Total time from shutdown until the port started forwarding was 30 seconds (27:27 to 27:57).
Step 7
To turn on PortFast, do the following:
2900XL#
conf t
Enter configuration commands, one per line. End with CNTL/Z.
2900XL(config)#
interface fastEthernet 0/1
2900XL(config-if)#
spanning-tree portfast
2900XL(config-if)#
exit
2900XL(config)#
exit
2900XL#
