Cisco switches use uplink fast to improve the convergence time of the STP due to an uplink failure. The UplinkFast feature is supported on Cisco Catalyst 4500/4000, 5500/5000, and 6500/6000 series switches running CatOS. This feature is also supported on Catalyst 4500/4000 and 6500/6000 switches that run Cisco IOS® System Software and 2900 XL/3500 XL, 2950, 3550, 3560 and 3750 series switches. Uplink fast is only recommended to be used for switches with blocked ports, typically at the access-layer because it is designed to be run for a switch that has at least one backup root port. This feature is not for use in switches that do not have a backup root port. To enable Uplink fast on a CatOS switch use the A>(enable) set spantree uplinkfast enable command. To enable Uplink fast on an IOS use the A> (config)#spanning-tree uplinkfast command.

According to the Cisco website (http://www.cisco.com/warp/public/473/51.html) UplinkFast has the
following limitations:
Uplink fast does not do the fast transition during a High Availability supervisor switchover on 6500/6000 switches that run CatOS. When the root port is lost on failed-resetting supervisor, the situation after a switchover is similar to when the switch boots up the first time because you do not sync the root port information between Supervisors. High Availability (HA) maintains only spanning tree port state, not the root port information, so when the HA switchover occurs, the new sup has no idea that it has lost a port on one of the uplink ports of the failed supervisor. A common workaround is the use of a port channel (EtherChannel). Root port status is maintained when a Port Channel is built across both supervisors, 1/1-2/1 or 1/2-2/2, for example, or root port is on the port of any Line Card. As no spanning tree topology change occurs when failing-resetting the active supervisor, no UplinkFast transition is necessary

Uplink fast does not do the fast transition during an RPR or RPR+ switchover on a 6500/6000 switch that runs Cisco IOS System Software. There is no workaround because Layer 2 port must go through spanning tree convergence states of listening, learning, and forwarding.  Cisco IOS Software on 6500/6000 does not implement generation of dummy multicast packets after uplinkfast transition for the update of CAM tables, refer to Cisco bug ID CSCdm65881 ( registered customers only) .

Uplink fast implementation on gigastack of 2900/3500XL/2950/3550/3560/3750 is called Cross Stack Uplink Fast Feature (CSUF), general UplinkFast feature on gigastack setup is not supported.  CSUF does not implement generation of dummy multicast packets after UplinkFast transition for the update of CAM tables.

Do not change spanning tree priority on the switch when UplinkFast is enabled because, it depends on the platform, and it can cause UplinkFast feature to be disabled, or it can cause a loop as the UplinkFast feature automatically changes the priority to a higher value in order to prevent the switch from becoming Root Bridge.

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Setting uplinkfast on a Cisco switch

Cisco’s answer to connectivity delays is port fast. When port fast is enabled it can help reduce the time it takes a PC to get a response. For example, if a Pc usually receives a response from the network in 30 to 35 seconds, enabling port fast may cut it down to five or six seconds. A few reasons that port delays occur are if STP is enabled, if there is EtherChannel negotiation going on, or in the link speed/duplex negotiations are taking time. Many users will give up on attempts to connect even before the port has received the data packet. This is why enabling port fast is beneficial.

However, you must be careful when enabling port fast that the switch is only connected to one device as to avoid creating a network loop where information will get lost and keep circling. To enable port fast in the interface configuration mode first use the following command ciscoswitch(config-if)# switchport mode access  to force switchport mode to access. Then use this command ciscoswitch(config-if)# spanning-tree portfast  to enable port fast.

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Setting portfast on a cisco switch

Backbonefast is a Cisco feature that can save up to 20 seconds when a switch recovers from an indirect link failure. For backbone fast to work it must be enable on all switches of the bridge network. Backbone fast can be enabled in both the CatOS and IOS switches.  Indirect link failures casue delays when STP invalidates information deemed wrong due to a failure. How STP does this is it waits for max-age, backbone fast gets rid of the max-age delay.

In order to get rid of the delay backbone fast does two things, it introduces the ability the detect an indirect link failure as soon as possible, and it creates a mechanism to check if BPDU information stored on a port is still valid. To enable backbone fast on a CatOS switch use the Console> (enable) set spantree backbonefast enable command. To enable backbone fast on an IOS switch use the CAT-IOS# configure terminal, then CAT-IOS(config)# spanning-tree backbonefast, then CAT-IOS(config)# end, then the CAT-IOS# commands.

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Setting backbonefast on a Cisco switch

Password recovery is possible and can be done following the procedure described below. Note that the procedure below is only for the Cisco Catalyst Layer 2 fixed configuration switches 2900XL/3500XL, 2940, 2950/2955, 2960, and 2970 Series, as well as the Cisco Catalyst Layer 3 fixed configuration switches 3550, 3560, and 3750 Series.

Password Recovery/Resetting
1. A terminal or a PC with terminal emulation should be attached to the console port with the following
terminal settings
A.Bits per second – 9600
B.Data Bits: 8
C.Parity: None
D.Stop Bits: 1
E.Flow Control: Xon / Xoff
2. Unplug the power cable and power on the switch
3. Go to the switch:prompt by
A.For 2900XL, 3500XL, and 3550 release the Mode button when the LED above Port 1x goes out
B.For 2940, 2950 release the Mode button after 5 seconds when the status LED goes out, the SYST
LED should be amber
C.For 2960,2970 release the Mode button when the SYST LED blinks amber and then turns solid
green, the SYST LED should blink green
D.For 3560, 3750 release the Mode button after 15 seconds when the SYST LED turns solid green,
the SYST LED should blink green.
4. Type the flash_init command
5. Type the load_helper command
6. Type the dir_flash: command
7. Type the rename flash:config.text flash:config.old which will rename the configuration file
8. Now type the boot command to load the system
9. When prompted to abort the initial configuration dialog answer with n
10. Follow the on screen directions answering with n and pressing [enter]
11. Type the en command to enter enable mode.
12. Type the rename flash:config.old flash:config.text command to rename the file to the old name
13. Type the copy flash:config.text system:running-config command to copy the configuration file into
memory
14. Type the conf t command to start overwriting passwords
A.Enable secret <secret password>
B.Enable password <enable password>
C.Line vty 0 15, then password <vty password> then login
D.Line con 0, then password <console password>
15. Type the write memory command to write the running configuration to the configuration file

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Reset passwords on a catalyst switch

Show commands are used as one time commands to show various properties or pieces of information about the current configuration on a system. Before knowing the actual show commands, there are certain fundamental rules to keep in mind; first off, all commands use a command line interface similar to MS DOS. All commands have a distinctive phrase to start them off; in this case it is that show comes before any command you give. Operations and commands vary from device to device; in this instance we are using Catalyst 3500XL commands. Commands must be typed or copied into the interface; they can not be done by pressing a GUI.  Pressing the [enter] key after typing instructs the system to execute the command.

The following some basic show commands:
show running-config is used to show the memory status
show interfaces is used to display specific information about all interfaces
show interfaces <interface name> is used to display specific information about a particular interface
show ip is used to display the IP configuration of the switch
show Mac-address-table is used to show the MAC addresses of devices connected to the switch
show VLAN  is used to show the enabled VLANs statuses
show VLAN-membership is used to show the membership of VLANs on all ports
show spantree 1 is used to show complete information on the spanning tree protocol 1

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Basic show commands for IOS