Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Community Member

spantree blocing question

Now, my two 3548 switchs each have two trunk uplink connectting to core 6509

switch,the two link are made into port channel.But I find that in one 3548, one

link's spantree status is blocking and the other is forwarding. In the other 3845s two link's spantree status is fordwarding. Why ?

the 6509 informaiton as following:

Port Mode Encapsulation Status Native vlan

4/2 nonegotiate dot1q trunking 1 (to 3548_1 G0/1)

4/3 nonegotiate dot1q trunking 1 (to 3548_2 G0/1)

5/2 nonegotiate dot1q trunking 1 (to 3548_1 G0/2)

5/3 nonegotiate dot1q trunking 1 (to 3548_2 G0/2)

Port Vlan Port-State Cost Prio Portfast Channel_id

4/2 1 forwarding 4 32 disabled 0

4/3 1 forwarding 4 32 disabled 0

5/2 1 blocking 4 32 disabled 0

5/3 1 forwarding 4 32 disabled 0

set spantree priority 8192 1

set spantree priority 8192 76

set port channel 4/2,5/2 386

set port channel 4/3,5/3 387

set trunk 4/2 nonegotiate dot1q 1-1005,1025-4094

set trunk 4/3 nonegotiate dot1q 1-1005,1025-4094

set trunk 5/2 nonegotiate dot1q 1-1005,1025-4094

set trunk 5/3 nonegotiate dot1q 1-1005,1025-4094

the 3548 informaiton as following:

sh spanning-tree interface g0/1

Interface Gi0/1 (port 67) in Spanning tree 1 is FORWARDING

Port path cost 4, Port priority 128

Designated root has priority 8192, address 0001.c74e.8000

Designated bridge has priority 32768, address 0005.32f5.8280

Designated port is 67, path cost 19

Timers: message age 0, forward delay 0, hold 0

BPDU: sent 690720, received 99

Interface Gi0/1 (port 67) in Spanning tree 76 is FORWARDING

Port path cost 4, Port priority 128

Designated root has priority 8192, address 00d0.00cf.3c4b

Designated bridge has priority 8192, address 00d0.00cf.3c4b

Designated port is 194, path cost 0

Timers: message age 1, forward delay 0, hold 0

BPDU: sent 5, received 365139

sh spanning-tree interface g0/2

Interface Gi0/2 (port 75) in Spanning tree 1 is FORWARDING

Port path cost 4, Port priority 128

Designated root has priority 8192, address 0001.c74e.8000

Designated bridge has priority 32768, address 0005.32f5.8280

Designated port is 75, path cost 19

Timers: message age 0, forward delay 0, hold 0

BPDU: sent 689667, received 14

Interface Gi0/2 (port 75) in Spanning tree 76 is BLOCKING

Port path cost 4, Port priority 128

Designated root has priority 8192, address 00d0.00cf.3c4b

Designated bridge has priority 8192, address 00d0.00cf.3c4b

Designated port is 2, path cost 0

Timers: message age 1, forward delay 0, hold 0

BPDU: sent 2, received 365135

3 REPLIES
Cisco Employee

Re: spantree blocing question

Hi King,

Can you post the configuration for your 3500Xl also?

Ankur

Bronze

Re: spantree blocing question

hi

can you post the (show port channel X)

where X is 4/2, 4/3, 5/2, 5/3 separately from your 6509.

it seems that the etherchannel does not form!!!

channel-id is 0 as you posted!!!

Re: spantree blocing question

The way I imagine your network from your description, you now have 4 bridges in a ring. One link needs to be blocked, not two. If you add a third access bridge, a second port will block. If you add a link between the two core, another link will block, etc...

Regards,

Francois

146
Views
0
Helpful
3
Replies
CreatePlease to create content