12-30-2024 06:47 AM - edited 12-30-2024 07:14 AM
Gi1/1/1 Root FWD 20000 128.49 P2p
Po1 Desg FWD 2000 128.2281 P2p
both are connected to the root bridge, which is a pair of 9500's. with each port connected to a different switch. G1/1/1 goes to core 1, with g1/1/2 going to core 2. trying to move them both to po1
Shouldn't the lowest cost be the root port?
I want to make the root port the port channel, so I can seamlessly add g1/1/1 to the port channel without spanning tree recalculating and taking the link down.
12-30-2024 06:51 AM
No friend not always'
If Port g1/1/1 receives bpdu from SW have lower mac then it will elect as root port.
The port cost use as tie breaker when both port receive bpdu from same SW
MHM
12-30-2024 06:56 AM
We need more information. We need to see the topology at least.
12-30-2024 07:06 AM
they are both directly connected to the root bridge, which is a pair of 9500's
12-30-2024 07:14 AM - edited 12-30-2024 07:15 AM
On the switch , can you run
show spanning-tree interface Gi1/1/1
12-30-2024 07:19 AM
core side is po32 and g1/0/3
show spanning-tree vlan 6
Twe1/0/3 Desg FWD 20000 128.195 P2p
Po32 Desg FWD 20000 32.2120 P2p
I tried to lower the priority to see if that would have an effect on the far side
12-30-2024 07:15 AM
check the mac address of 9500 you will see the bridge ID (mac + priorty) is different and then one connect to g1/1/1 have lowest
12-30-2024 07:33 AM
wait a min both port connect to both 9500 ?
if 9500 run stackwise virtual then
""The spanning-tree domain treats the StackWise Virtual pair as one bridge node instead of two.""
and if one SW connect to other (stackwise virtual) with two link, one link will be root/dst and other will be BLK
MHM
12-30-2024 07:35 AM
is the same same switch... the root bridge. Both ports are connected to the root bridge, which has only one mac address.
ILLINI-DC-CORE#show spanning-tree vlan 6
VLAN0006
Spanning tree enabled protocol rstp
Root ID Priority 4102
Address 3473.2dd9.db20
This bridge is the root
12-30-2024 07:40 AM
ILLINI-DC-CORE#show spanning-tree vlan 6 <<<- this STP from both C9500
VLAN0006
Spanning tree enabled protocol rstp
Root ID Priority 4102
Address 3473.2dd9.db20
This bridge is the root
And below for SW-X connect to both C9500 Stackwise ?
Gi1/1/1 Root FWD 20000 128.49 P2p
Po1 Desg FWD 2000 128.2281 P2p
if above correct then share the
show portchannel summary in SW-X
MHM
12-30-2024 07:57 AM
12-30-2024 08:02 AM
below for C9200 connect to two C9500, just confirm ?
Gi1/1/1 Root FWD 20000 128.49 P2p
Po1 Desg FWD 2000 128.2281 P2p
12-30-2024 08:12 AM
This really is very simple. 1 9200 connected to a 9500 stack. We connect g1/1/1 to core1 and 2/1/1 to core2. Used to be called a vss pair, and is now stackwise, maybe? But the 9500 pair is the spanning tree root. so virtually one switch plugged into one switch.
Why? Does it matter? But the answer is, we had one link in the past. G1/1/1 on the 9200 and we want to move to a portchannel. So the fiber guys ran a new pair and I created PO1 and started with he 2nd link with the idea being that we could change the spanning tree cost to prefer the port channel, then move the g1/1/1 into the portchannel without taking the network down in a hospital. I change the port cost on the edge, and the root port did not move. I changed the priority on the core, and the spanning tree root port did not move. I actually had this scenario on s CCNP test 12 years ago
12-30-2024 08:22 AM
PO1 in c9200 have one leg is connect to Core1 or Core2 ?
if it connect to Core1 then port must be BLK
if it connect to Core2 and Core1/2 run StackWise virtual (one virtual SW) and PO and G1/1/1 is FWD State, we have problem
the traffic from C9200 go to Core2 then vis SVL to Core1 and return to C9200 do you see it right ?
Sure Not, first stop to not make issue disable PO prevent storm
also before you use PO in C9200 is G1/1/1 and G2/1/1 both are FWD state ?
MHM
12-30-2024 08:50 AM
I hope idea is clear'
Sorry I will enjoy with my family new year eve so I will be unavailable from now until 2/1/2025.
Happy new year friend
Goodluck
MHM
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