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spanning tree problem

MARCELO MATURO
Level 1
Level 1

‎10-15-2002 01:11 PM - edited ‎03-02-2019 02:06 AM

There are 2 catalyst 5500 with 2 trunks, one an etherchannel (isl), the other an ATM OC3 ( lane trunk).

One of the switches is the root bridge of the tree ( it has priority 1, the other 5).

One of the vlan is blocking in the channel port, is forwarding through the ATM trunking in the root bridge switch.

How is possible that there would be blocking ports in the root bridge?

This is the show for the vlan that is blocking:

CATALYST1> (enable) sh spantree 5

VLAN 5

Spanning tree enabled

Spanning tree type ieee

Designated Root 00-02-18-ca-00-00

Designated Root Priority 1

Designated Root Cost 37

Designated Root Port 2/1

Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Bridge ID MAC ADDR 00-02-18-ca-00-04

Bridge ID Priority 1

Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Port Vlan Port-State Cost Priority Fast-Start Group-Method

--------- ---- ------------- ----- -------- ---------- ------------

1/1-2 5 blocking 2 0 disabled channel

2/1-2 5 forwarding 19 32 disabled redundancy

3/1 5 forwarding 100 32 disabled

3/15 5 forwarding 19 32 disabled

3/17 5 forwarding 19 32 disabled

3/18 5 forwarding 19 32 disabled

3/20 5 forwarding 19 32 disabled

3/22 5 forwarding 100 32 disabled

3/23 5 forwarding 19 32 disabled

3/24 5 forwarding 19 32 disabled

4/1 5 forwarding 5 32 disabled

5/1 5 forwarding 19 32 disabled

5/2 5 forwarding 19 32 disabled

5/7 5 forwarding 19 32 enabled

5/8 5 forwarding 19 32 disabled

5/12 5 forwarding 19 32 disabled

5/19 5 forwarding 19 32 disabled

5/23 5 forwarding 19 32 disabled

CATALYST1> (enable)

Thanks.

Marcelo

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4 Replies 4

steve.barlow
Level 7
Level 7

‎10-15-2002 02:11 PM

This switch is not root for vlan 5, hence he is blocking. This switch sees the root on port 2/1-2 (and the root has a different mac than the local switch). The blocked port is 1/1-2. Ports 1/1-2 are blocked, ports 2/1-2 are forwarding. The other end of the link is root, and it is still in forwarding state on both trunks. If the secondary switch didn't block one end, there would be a loop.

This is the potential loop without the block:

switchAport1/1-2 -(x)------switchBport1/1-2

switchAport2/1-2 -------switchBport2/1-2

(where x is the blocked ports)

Steve

0 Helpful

MARCELO MATURO
Level 1
Level 1
In response to steve.barlow

‎10-16-2002 06:39 AM

Steve, You say is true. But see something:

This is the output for sh modules:

Mod MAC-Address(es) Hw Fw Sw

--- -------------------------------------- ------ ---------- -----------------

1 00-02-18-ca-00-00 to 00-02-18-ca-03-ff 3.8 5.1(2) 5.1(1)

2 00-60-3e-cc-33-bc 2.4 1.3 11.3(8)WA4(11a) 3.2(13)

3 00-01-63-53-a2-88 to 00-01-63-53-a2-9f 3.3 4.3(1) 5.1(1)

4 00-e0-1e-91-de-2c to 00-e0-1e-91-de-2d 7.7 20.18 12.0(5)

5 00-04-28-77-fd-f8 to 00-04-28-77-fe-0f 1.1 4.5(2) 5.1(1)

Mod Sub-Type Sub-Model Sub-Serial Sub-Hw

--- -------- --------- ---------- ------

1 EARL 1+ WS-F5511 0019515344 1.1

CATALYST1> (enable)

The system mac is the same the is showed for the root bridge in vlan 5.

And this switch is the only with priority 1 en the lan.

See the show spantree for the other sw:

C_5509_GRANJA_SOLIS> (enable) sh spantree 5

VLAN 5

Spanning tree enabled

Spanning tree type ieee

Designated Root 00-02-18-ca-00-00

Designated Root Priority 1

Designated Root Cost 36

Designated Root Port 4/1

Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Bridge ID MAC ADDR 00-02-18-ca-f8-04

Bridge ID Priority 5

Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Port Vlan Port-State Cost Priority Fast-Start Group-Method

--------- ---- ------------- ----- -------- ---------- ------------

1/1-2 5 forwarding 2 32 disabled channel

2/1 5 forwarding 10 32 disabled

2/2 5 forwarding 10 32 disabled

2/3 5 forwarding 10 32 disabled

2/4 5 forwarding 13 32 disabled

2/5 5 forwarding 10 32 disabled

2/7 5 forwarding 10 32 disabled

2/9 5 forwarding 10 32 disabled

2/10 5 forwarding 10 32 disabled

3/1 5 forwarding 10 32 disabled

3/2 5 forwarding 10 32 disabled

3/3 5 forwarding 10 32 disabled

3/4 5 forwarding 10 32 disabled

3/6 5 forwarding 10 32 disabled

3/7 5 forwarding 10 32 disabled

3/8 5 forwarding 10 32 disabled

3/9 5 forwarding 10 32 disabled

3/12 5 forwarding 10 32 disabled

3/13 5 forwarding 19 32 disabled

3/14 5 forwarding 19 32 disabled

3/18 5 forwarding 19 32 disabled

3/19 5 forwarding 19 32 disabled

3/21 5 forwarding 19 32 disabled

3/22 5 forwarding 19 32 enabled

3/23 5 forwarding 19 32 disabled

4/1-2 5 forwarding 18 32 disabled redundancy

5/1 5 forwarding 5 32 disabled

C_5509_GRANJA_SOLIS> (enable)

I don´t understand what is happening.

Marcelo

0 Helpful

steve.barlow
Level 7
Level 7
In response to MARCELO MATURO

‎10-16-2002 03:30 PM

Your right this looks strange.

CATALYST1 1/1-2 -x--------1/1-2 C_5509_GRANJA_SOLIS

CATALYST1 2/1-2 ----------4/1-2 C_5509_GRANJA_SOLIS

CATALYST1 sees mac 00-02-18-ca-00-00 on port 2/1 and C_5509_GRANJA_SOLIS sees it on 4/1. Yet that mac is on mod 1 of CATALYST1. Is this only for vlan 5 or other vlans?

They are both in the same vtp domain and have both trunk ends for both trunks set as the same trunking mode?

I am leaning towards the lane trunk or a bug as the fault.

Steve

0 Helpful

MARCELO MATURO
Level 1
Level 1
In response to steve.barlow

‎10-17-2002 01:07 PM

Both swtiches are in the same vtp domain. Both trunk ends are set as ISL. For the other vlans don't happen the same. For example vlan 1:

CATALYST1> (enable) sh spantree 1

VLAN 1

Spanning tree enabled

Spanning tree type ieee

Designated Root 00-02-18-ca-00-00

Designated Root Priority 1

Designated Root Cost 0

Designated Root Port 1/0

Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Bridge ID MAC ADDR 00-02-18-ca-00-00

Bridge ID Priority 1

Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Port Vlan Port-State Cost Priority Fast-Start Group-Method

--------- ---- ------------- ----- -------- ---------- ------------

1/1-2 1 forwarding 2 0 disabled channel

2/1-2 1 forwarding 19 33 disabled redundancy

3/24 1 forwarding 19 32 disabled

4/1 1 forwarding 5 32 disabled

5/3 1 forwarding 19 32 disabled

5/10 1 forwarding 19 32 disabled

5/11 1 forwarding 19 32 disabled

the other:

C_5509_GRANJA_SOLIS> (enable) sh spantree 1

VLAN 1

Spanning tree enabled

Spanning tree type ieee

Designated Root 00-02-18-ca-00-00

Designated Root Priority 1

Designated Root Cost 12

Designated Root Port 1/1-2

Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Bridge ID MAC ADDR 00-02-18-ca-f8-00

Bridge ID Priority 5

Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec

Port Vlan Port-State Cost Priority Fast-Start Group-Method

--------- ---- ------------- ----- -------- ---------- ------------

1/1-2 1 forwarding 12 32 disabled channel

2/1 1 forwarding 10 32 disabled

2/6 1 forwarding 10 32 disabled

2/12 1 forwarding 10 32 disabled

3/4 1 forwarding 10 32 disabled

3/7 1 forwarding 10 32 disabled

3/10 1 forwarding 10 32 disabled

3/16 1 forwarding 19 32 disabled

3/17 1 forwarding 19 32 disabled

3/20 1 forwarding 19 32 disabled

3/23 1 forwarding 19 32 disabled

4/1-2 1 blocking 18 32 disabled redundancy

5/1 1 not-connected 5 32 disabled

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