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alex_ciobanu
Beginner

Uplinkfast in RSTP

Hello,

Is Uplinkfast enabled in RSTP ?

S1#show spanning-tree

VLAN0001

  Spanning tree enabled protocol rstp

S1#show spanning-tree uplinkfast

UplinkFast is enabled but inactive in rapid-pvst mode

I see it says is enabled, but inactive, but yet there are some ports in ALT state. However, if it should be enabled by default, it shouldn't modify the ports costs to high values, and also the bridge priority ?

1 ACCEPTED SOLUTION

Accepted Solutions
Peter Paluch
Hall of Fame Cisco Employee

Hi Alex,

RSTP natively contains improvements similar to UplinkFast and BackboneFast that can not be disabled. You do not need to enable anything special to already have the necessary functionality. The UplinkFast and BackboneFast will be reported as disabled in your output because RSTP uses its own implementations of the same improvements. In fact, it is not appropriate to try to enable UplinkFast and BackboneFast when running RSTP.

Best regards,

Peter

View solution in original post

3 REPLIES 3
Peter Paluch
Hall of Fame Cisco Employee

Hi Alex,

RSTP natively contains improvements similar to UplinkFast and BackboneFast that can not be disabled. You do not need to enable anything special to already have the necessary functionality. The UplinkFast and BackboneFast will be reported as disabled in your output because RSTP uses its own implementations of the same improvements. In fact, it is not appropriate to try to enable UplinkFast and BackboneFast when running RSTP.

Best regards,

Peter

View solution in original post

Reza Sharifi
Hall of Fame Expert

Hi,

In addition to what Peter noted, when uplink fast is enable the switch priority is changed.

See example

Before uplink fast is enabled

Switch(config)#do sh spann

VLAN0001

  Spanning tree enabled protocol ieee

  Root ID    Priority    32769

             Address     001b.5400.3380

             This bridge is the root

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority   32769  (priority 32768 sys-id-ext 1)

             Address     001b.5400.3380

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type

------------------- ---- --- --------- -------- --------------------------------

Gi1/0/1             Desg FWD 19        128.1    P2p

after uplink fast is enabled

Switch(config)#spann

Switch(config)#spanning-tree up

Switch(config)#spanning-tree uplinkfast

Switch(config)#do sh spann             

VLAN0001

  Spanning tree enabled protocol ieee

  Root ID    Priority    49153

             Address     001b.5400.3380

             This bridge is the root

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    49153  (priority 49152 sys-id-ext 1)

             Address     001b.5400.3380

             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

             Aging Time  300 sec

  Uplinkfast enabled

Interface           Role Sts Cost      Prio.Nbr Type

------------------- ---- --- --------- -------- --------------------------------

Gi1/0/1             Desg FWD 3019      128.1    P2p

Switch(config)#

HTH

alex_ciobanu
Beginner

Yes, I know, that happens in traditional mode stp, I was reffering to RSTP.

However, things are clear now, UPlinkfast does not exist in RSTP, but simmilar implementations are available by default.