10-30-2012 09:15 PM - edited 03-07-2019 09:46 AM
Please explain the output of show spanning-tree summary:
SW1-R3#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 108c.cfb6.ab00
Cost 19
Port 15 (FastEthernet0/13)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 108c.cfb6.9a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.3 P2p
Fa0/5 Desg FWD 19 128.7 P2p
Fa0/13 Root FWD 19 128.15 P2p
Fa0/14 Altn BLK 19 128.16 P2p
Fa0/15 Altn BLK 19 128.17 P2p
Fa0/13-15 connected to the switch SW-R2
I can not understand Fa0/14-15 Port role is Alt, because the role of Alternative port was introduced in RSRP. In our case, STP in PVST Mode.
Can you explain this please?
Solved! Go to Solution.
10-30-2012 10:35 PM
Hi,
Please see the below discussion which explain about your query
It is true that the port roles were introduced with RSTP. However, they definitely make sense for STP (for instance, the difference between an alternate and a backup port is useful to uplinkfast, and it's also nice to see clearly what the root port is) so we decided to display the role in STP mode also (something we did not do for CatOS afaik)
Running STP nowadays should be in fact running RSTP in STP compatibility mode. And in that case, the switch would definitely display the RSTP roles.
Refer the below discussion:
https://supportforums.cisco.com/message/581353#581353
Regards,
Aru
*** Please rate if the post is useful ***
10-30-2012 10:35 PM
Hi,
Please see the below discussion which explain about your query
It is true that the port roles were introduced with RSTP. However, they definitely make sense for STP (for instance, the difference between an alternate and a backup port is useful to uplinkfast, and it's also nice to see clearly what the root port is) so we decided to display the role in STP mode also (something we did not do for CatOS afaik)
Running STP nowadays should be in fact running RSTP in STP compatibility mode. And in that case, the switch would definitely display the RSTP roles.
Refer the below discussion:
https://supportforums.cisco.com/message/581353#581353
Regards,
Aru
*** Please rate if the post is useful ***
10-30-2012 10:50 PM
Thank you for a clear answer.
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