Spanning-tree port type

[schmidtjoe]

When I run the cli show spanning-tree vlan 1, I notice the port type is shr. What does shr stand for?

Switch#show spanning-tree vlan 1

VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32769
             Address     0c21.0d37.0b00
             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     0c21.0d37.0b00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/0               Desg FWD 4         128.1    Shr
Gi0/1               Desg FWD 4         128.2    Shr
Gi0/2               Desg FWD 4         128.3    Shr
Gi0/3               Desg FWD 4         128.4    Shr
Gi1/0               Desg FWD 4         128.5    Shr
Gi1/1               Desg FWD 4         128.6    Shr
Gi1/2               Desg FWD 4         128.7    Shr
Gi1/3               Desg FWD 4         128.8    Shr

[David Ruess]

Hello,

It means the port is believed to be connected to a shared segment (Shr). This could be a hub or wireless access point where multiple devices are seen or can be seen. Also if the port is operating in half-duplex the port could assume its a shard link like mentioned before of being attached to a hub or other device that operates in half-duplex.

Hope that helps

-David

[Kasun Bandara]

its for Half-duplex connections.

[paul driver · Accepted solution]

Hello
The port type in rstp is important for fast convergence (p2p/edge) 
RSTP port in shared mode will negate its fast convergence, it only "assumes" its port type by the duplex mode of the physical port (H/D= stp shared, F/D=stp P2P)

Example:
The physical port could be set to F/D but the stp link type set to shared and it will show as a Shr port in stp
or
The physical port could be set th H/D but the stp link type set to point-to-point and it will show up as a P2P port in stp 

So STP has no way of actually knowing what is connected to the switchport, it could be just a single host/another switch or a hub if its solely based on the duplex mode of the switchport, hence it suggested you actually set the stp port type (P2P/Edge-portfast/Shared) be it for the benefit of the network