I have two Dell PowerConnect switches I want to connect together via Port-Channel links (2 ethernet links).
Spanning tree is enabled on both switches, so therefore applied to all interfaces unless otherwise specified.
Here is the configuration I would expect to work, but doesn't.
Switch A - Dell 6248
interface ethernet 3/g21
channel-group 39 mode auto
interface ethernet 3/g22
channel-group 39 mode auto
interface port-channel 39
Switch B - Dell 5424
interface ethernet g18
channel-group 4 mode auto
interface ethernet g19
channel-group 4 mode auto
interface port-channel 4
As you can see there is no specific config applied to each port channel. When I connect everything up using this configuration, I get no communication between the two switches. Output of show spanning-tree follows:
Switch A - Dell 6248
Port ch39 Enabled
State: Discarding Role: Designated
Port id: 128.664 Port Cost: 10000
Port Fast: No (Configured: no ) Root Protection: No
Designated bridge Priority: 16384 Address: 40:00:00:25:64:25:B6:82
Designated port id: 128.664 Designated path cost: 0
CST Regional Root: 10:00:00:25:64:25:B6:91 CST Port Cost: 1000
Root Guard..................................... FALSE
Loop Guard..................................... FALSE
TCN Guard...................................... FALSE
BPDU: sent 1260, received 1226
Switch B - Dell 5424
Port ch4 enabled
State: forwarding Role: designated
Port id: 128.52 Port cost: 4
Type: P2P (configured:Auto ) RSTP Port Fast: No (configured:No)
Designated bridge Priority : 32768 Address: 00:23:ae:d6:a5:77
Designated port id: 128.52 Designated path cost: 4
Guard root: Disabled BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 3715, received 0
As you can see, with spanning tree enabled everywhere, Switch A's port-channel goes into discarding state.
If I disable spanning tree on Switch A communication between two switches works.
interface port-channel 39
spanning-tree disable
So two questions:
- Is there something I am missing in the config that I need to fix so spanning-tree will allow traffic through.
- Should I just disable spanning tree on the port-channel on Switch A and stop worrying about this?