CCIE Pursuit Blog

September 15, 2007

3560 to 3560 Orange Lights

Filed under: Cisco,Cisco Certification,Home Lab,IOS,Switching — cciepursuit @ 3:57 pm

CCIE Journey encountered some interesting lights on his 3560s while setting up his lab:

My four switches are connected as per IE’s layer 1 configuration. Now the three links that connect SW1 and SW2 on the two 3560’s were coming up weird on SW1. Interface fa 0/13 was showing green on both switches, but fa0/14-15 was showing orange on SW1.Once Trunking come up in the COD tonight it reminded me that 3560’s run Dynamic Auto by default. So I set Dynamic Desirable on links Fa 0/13-15 on SW2 and both orange led’s on SW1 went green again. Ok I thought that makes sense, but what doesn’t make sense is why was fa 0/13 green on SW1 if both sides were set to auto as well ? It is the little things that drive me…

I had an idea that this was due to STP blocking on the two non-root ports of sw1.  I wish that I could say that I thought of this not because I am a networking guru (not even close!), but the reason that this jumped into my skull is because of an annoying customer that I once had. 

The customer was at a location that were going to to upgrade to our standard 3750 switch stacks, but in the mean time were using 3560s “stacked” with crossover cables on redundant links between the switches in the “stack”.  Almost immediately he started paging out the network team because of “bad ports”.  It seemed that there were a couple of orange lights on the switchports.  I looked into the issue and told him that those ports were in spanning-tree blocking state and that was why the port lights were orange.  I told him that this was normal and would not affect the switches.  Of course the orange lights became legendary “bad ports” and every network blip at that site was immediately blamed on these ports.  Eventually, I “fixed” the problem by having the customer push the “Mode” button on the front of the switch.  This set the Mode to “DUPLX” and all of the port lights went green because all of the ports were running at full duplex.  Unfortunately, this only “worked” for a brief period of time because the Mode would eventually switch back to “STAT” and the blocking ports would become orange again.  😦

Anyhoo….I labbed up CCIE Journey’s scenario by defaulting ports fa0/13 – 15 on sw1 and sw2, then:

sw1#sh ver | i IOS
Cisco IOS Software, C3560 Software (C3560-IPSERVICESK9-M), Version 12.2(25)SEE2, RELEASE SOFTWARE (fc1)
sw1#sh run | b 0/13
interface FastEthernet0/13 <-ports have been defaulted
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
sw1#sh int status | b 0/13
Fa0/13                       connected    1          a-full  a-100 10/100BaseTX
Fa0/14                       connected    1          a-full  a-100 10/100BaseTX
Fa0/15                       connected    1          a-full  a-100 10/100BaseTX

sw1#sh sp v 1

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    32769
             Address     0012.009c.ca00
             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     0012.018f.d580
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
—————- —- — ——— ——– ——————————–
Fa0/13          Root FWD 19      128.15   P2p
Fa0/14           Altn BLK 19        128.16   P2p
Fa0/15           Altn BLK 19        128.17   P2p
************************

sw2 is the root switch: 
sw2#sh ver | i IOS
Cisco IOS Software, C3560 Software (C3560-IPSERVICESK9-M), Version 12.2(25)SEE2, RELEASE SOFTWARE (fc1)
sw2#sh run | b 0/13
interface FastEthernet0/13 <-ports have been defaulted
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!

sw2#sh int status | b 0/13
Fa0/13                       connected    1          a-full  a-100 10/100BaseTX
Fa0/14                       connected    1          a-full  a-100 10/100BaseTX
Fa0/15                       connected    1          a-full  a-100 10/100BaseTX

sw2#sh sp v 1

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    32769
             Address     0012.009c.ca00
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
             Address     0012.009c.ca00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 15

Interface        Role Sts Cost      Prio.Nbr Type
—————- —- — ——— ——– ——————————–
Fa0/13           Desg FWD 19        128.15   P2p
Fa0/14           Desg FWD 19        128.16   P2p
Fa0/15           Desg FWD 19        128.17   P2p
**************

sw2 is the root.  The ports are all FWD (therefore all green).  sw1 is non-root, fa1/13 is the root port and therefore forwarding (green), the other two are blocking(orange).

We can test whether the lights are orange due to STP blocking two ways:

1) Make sw1 the root and see if its lights all go green, while sw2’s fa0/14 and fa0/15 go orange.
2) Change the root port on sw1 to fa0/14 and see if it goes green while fa0/13 goes orange.

Method 1:

sw1(config)#spanning-tree vlan 1 root primary
sw1(config)#^Z

sw1#sh sp v 1

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    24577
             Address     0012.018f.d580
             This bridge is the root <-sw1 is now the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24577  (priority 24576 sys-id-ext 1)
             Address     0012.018f.d580
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 15

Interface        Role Sts Cost      Prio.Nbr Type
—————- —- — ——— ——– ——————————–
Fa0/13           Desg FWD 19        128.15   P2p
Fa0/14           Desg FWD 19        128.16   P2p
Fa0/15           Desg FWD 19        128.17   P2p

sw2#sh sp v 1

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    24577
             Address     0012.018f.d580
             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     0012.009c.ca00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
—————- —- — ——— ——– ——————————–
Fa0/13           Root FWD 19        128.15   P2p <-note
Fa0/14           Altn BLK 19        128.16   P2p
Fa0/15           Altn BLK 19        128.17   P2p

Now all three of sw1’s port are green, while fa0/13 on sw2 is green and fa0/14 – 15 are orange.  I don’t have photos, so you’ll have to trust me on this  🙂 

Method 2 (after making sw2 the root again):

sw1#sh sp v 1

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    32769
             Address     0012.009c.ca00
             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     0012.018f.d580
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 15

Interface        Role Sts Cost      Prio.Nbr Type
—————- —- — ——— ——– ——————————–
Fa0/13           Root FWD 19        128.15   P2p
Fa0/14           Altn BLK 19        128.16   P2p
Fa0/15           Altn BLK 19        128.17   P2p

sw1(config-if)#int fa0/14
sw1(config-if)#spanning-tree vlan 1 cost 1
sw1(config-if)#do sh sp v 1

VLAN0001
  Spanning tree enabled protocol ieee
  Root ID    Priority    32769
             Address     0012.009c.ca00
             Cost        1
             Port        16 (FastEthernet0/14)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
             Address     0012.018f.d580
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
—————- —- — ——— ——– ——————————–
Fa0/13           Altn BLK 19        128.15   P2p
Fa0/14           Root FWD 1         128.16   P2p <-this is now green
Fa0/15           Altn BLK 19        128.17   P2p

Now fa0/13 and fa0/15 on sw1 are orange and fa0/14 is green.  All three ports on sw2 are still green.

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3 Comments »

  1. It is the little things that drive me insane and at this rate the lab will be 3 years away :).

    Comment by Carl — September 15, 2007 @ 9:13 pm | Reply

  2. I hear ya. It seems that the more I learn, the more I realize that I do not know. 😦

    On the other hand, being drawn in by the “little things” generally will lead to a better understanding of the whole. I might seem like it will take longer to reach your goal, but you’ll probably be better prepared.

    Comment by cciepursuit — September 16, 2007 @ 5:43 am | Reply

  3. Good info to know. Thanks for sharing!

    Comment by Abdelkrim — May 9, 2008 @ 3:09 am | Reply


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