Output of the show spantree Command Using an EtherChannel

Jul 08,2008 by admin

Output of the show spantree Command Using an EtherChannel

Switch1 (enable) show spantree

VLAN 1

Spanning tree mode          PVST+

Spanning tree type          ieee

Spanning tree enabled



Designated Root             00-05-74-18-04-80

Designated Root Priority    4097

Designated Root Cost        0

Designated Root Port        1/0

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



Bridge ID MAC ADDR          00-05-74-18-04-80

Bridge ID Priority          4097  (bridge priority: 4096, sys ID ext: 1)

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



Port                     VLAN Port-State    Cost      Prio Portfast Channel_id

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

10/13-16                 1    forwarding            8   32 disabled 871

The valid EtherChannel configurations are

Desirable-Desirable
Desirable-Auto
On-On
Off-Off

Cisco recommends Desirable-Desirable mode configuration for EtherChannel. This is beneficial because ports will actively negotiate setting up a channel and will allow the operation of PAgP. It is also recommended to leave Silent/Non-Silent parameters to their default values if UDLD is supported.

Table 4-3 describes the type of channel states that will develop depending on the configuration of the adjacent switches. Spanning tree shuts down (errdisable) channels that are misconfigured, as noted in Table 4-3.