02-16-2009 01:06 PM - edited 03-06-2019 04:04 AM
Hi all,
I have a topology like on the attachment. Please check it out...
I have four VLANs (10,20,30,40). The Core 1 is the root primary for the 10 and 20 VLAN.
The Core 2 is the root primary for the 30,40 VLAN.
On the SW1, the output of command "show spanning-tree root" shows me that the port g0/49 is the root port for all VLANs.
Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
VLAN0010 24584 0019.55f2.f000 8 2 20 15 Gi0/49
VLAN0020 24585 0019.55f2.f000 8 2 20 15 Gi0/49
VLAN0030 24586 0019.55f2.edc0 4 2 20 15 Gi0/49
VLAN0040 24587 0019.55f2.edc0 4 2 20 15 Gi0/49
The output on SW2 shows me that the port 0/52 is the root port for all VLANs.
Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
VLAN0010 24584 0019.55f2.f000 4 2 20 15 Gi0/52
VLAN0020 24585 0019.55f2.f000 4 2 20 15 Gi0/52
VLAN0030 24586 0019.55f2.edc0 8 2 20 15 Gi0/52
VLAN0040 24587 0019.55f2.edc0 8 2 20 15 Gi0/52
Does it mean that the traffic is flowing through this ports?
The traffic wouldn't be balanced bettween the uplinks, on both switches?
I mean, on SW 1, wouldn't the VLAN 10 and 20 traffic flow through the interface G0/49 and the VLAN 30 and 40 traffic flow throught the interface G0/52?
Thanks
Tauer
Solved! Go to Solution.
02-16-2009 01:35 PM
i agreew ith edeson
just go to the interface g0/52 and increase the cost for those vlans
try the following command
interface gig0/52
spanning-tree vlan 10,20 cost 100
this way the cost through g0/49 will be less for those vlans then will be chosen
good luck
if helpful Rate
02-16-2009 01:14 PM
You did noticed the MAC-Address is different on Vlan 30,40 from Vlan 10,20?
What's the output telling you that it knows the root port via that switchport but the MAC-Address indicates what switch is the root for that Vlan.
HTH,
__
Edison.
02-16-2009 01:18 PM
Hi Edison,
I did.
But, the VLAN 10 and 20 on SW 2, wouldn't flow out the interface G0/49, instead 0/52?
Thanks
Tauer
02-16-2009 01:23 PM
The cost is lower via Core 2 <-> Core 1 than SW1 <-> Core 1.
Please post the show spanning-tree from SW2 and SW1.
02-16-2009 01:35 PM
i agreew ith edeson
just go to the interface g0/52 and increase the cost for those vlans
try the following command
interface gig0/52
spanning-tree vlan 10,20 cost 100
this way the cost through g0/49 will be less for those vlans then will be chosen
good luck
if helpful Rate
02-16-2009 01:39 PM
Hi Edson,
follow the output on SW1.
SW 1
VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 24584
Address 0019.55f2.f000
Cost 8
Port 49 (GigabitEthernet0/49)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32776 (priority 32768 sys-id-ext 8)
Address 0019.55e0.f680
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/52 Altn BLK 4 128.48 P2p
Gi0/49 Root FWD 4 128.49 P2p
VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 24585
Address 0019.55f2.f000
Cost 8
Port 49 (GigabitEthernet0/49)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32777 (priority 32768 sys-id-ext 9)
Address 0019.55e0.f680
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/52 Altn BLK 4 128.48 P2p
Gi0/49 Root FWD 4 128.49 P2p
VLAN0030
Spanning tree enabled protocol ieee
Root ID Priority 24586
Address 0019.55f2.edc0
Cost 4
Port 49 (GigabitEthernet0/49)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 0019.55e0.f680
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/52 Desg FWD 4 128.48 P2p
Gi0/49 Root FWD 4 128.49 P2p
VLAN0040
Spanning tree enabled protocol ieee
Root ID Priority 24587
Address 0019.55f2.edc0
Cost 4
Port 49 (GigabitEthernet0/49)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32779 (priority 32768 sys-id-ext 11)
Address 0019.55e0.f680
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/52 Desg FWD 4 128.48 P2p
Gi0/49 Root FWD 4 128.49 P2p
02-16-2009 01:40 PM
SW 2
_________
VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 24584
Address 0019.55f2.f000
Cost 4
Port 52 (GigabitEthernet0/52)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32776 (priority 32768 sys-id-ext 8)
Address 001c.0e11.6480
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- -------------------------------
Gi0/49 Desg FWD 4 128.48 P2p
Gi0/52 Root FWD 4 128.52 P2p
VLAN0020
Spanning tree enabled protocol ieee
Root ID Priority 24585
Address 0019.55f2.f000
Cost 4
Port 52 (GigabitEthernet0/52)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32777 (priority 32768 sys-id-ext 9)
Address 001c.0e11.6480
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- -------------------------------
Gi0/49 Desg FWD 4 128.48 P2p
Gi0/52 Root FWD 4 128.52 P2p
VLAN0030
Spanning tree enabled protocol ieee
Root ID Priority 24586
Address 0019.55f2.edc0
Cost 8
Port 52 (GigabitEthernet0/52)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 001c.0e11.6480
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- -------------------------------
Gi0/49 Altn BLK 4 128.48 P2p
Gi0/52 Root FWD 4 128.52 P2p
VLAN0040
Spanning tree enabled protocol ieee
Root ID Priority 24587
Address 0019.55f2.edc0
Cost 8
Port 52 (GigabitEthernet0/52)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32779 (priority 32768 sys-id-ext 11)
Address 001c.0e11.6480
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- -------------------------------
Gi0/49 Altn BLK 4 128.48 P2p
Gi0/52 Root FWD 4 128.52 P2p
02-16-2009 01:54 PM
Tauer,
In your case, the cost is equal. There are other variables to determine the root port:
When selecting the root port on a switch stack, spanning tree follows this sequence:
-Selects the lowest root bridge ID
-Selects the lowest path cost to the root switch
-Selects the lowest designated bridge ID
-Selects the lowest designated path cost
-Selects the lowest port ID
It could be the Cores have a lower bridge ID than the access switches.
HTH,
__
Edison.
02-16-2009 02:04 PM
Hi Edson,
My Core Switches have the follow priority... It forces them to have a lower ID, than access switches... So they have the lowest root bridge ID...
CORE 1
spanning-tree mode pvst
spanning-tree extend system-id
spanning-tree vlan 10-20 priority 24576
spanning-tree vlan 30-40 priority 28672
CORE 2
spanning-tree mode pvst
spanning-tree extend system-id
spanning-tree vlan 10-20 priority 28672
spanning-tree vlan 30-40 priority 24576
02-16-2009 02:24 PM
Then, that answers your question/dilemma.
__
Edison.
Please rate helpful posts
02-17-2009 04:41 AM
hi Edison,
I didn't figure out yet..
With this configuration, wouldn't the traffic from VLAN 30,40, on SW 1, flow out throught the port 0/52?...and only traffic from VLAN 10,20 flow out through port 0/49?
Thanks
Tauer
02-16-2009 01:31 PM
Tauer,
What is the type of connection between Core-01 and Core-02? Is it Giga Interface?
HTH
Mohamed
02-16-2009 01:41 PM
Hi Mohamed,
All the connections are GigabitEthernet (Fiber).
02-16-2009 02:25 PM
Hi Tauer
the link cost shown abov look the same
however i need to chec kis the inter switch trunk is etherchannel
??
also if you try to change the port cost for those vlans on that port i as i mentioned above you will get it working as you want
good luck
02-17-2009 08:22 AM
Hi marwanshawi,
your advice cleared my mind and solved the problem...
Thank you
Tauer
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