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Port error on Switch 2950

Hi,

I need help please.

I just got a CPE as MetroEthernet and if I connect a computer directly to the CPE, i get internet access fine.

But if I connect the CPE to the Cisco 2950 Switch, i get this error:

IT_2950#sh sp
IT_2950#sh spanning-tree

VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32769
             Address     0015.2b7e.2d80
             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     0015.2b7e.2d80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/22           Desg FWD 19        128.22   P2p
Fa0/23           Desg BKN*19        128.23   P2p *PVID_Inc

The port that Im using to connect is Fast 0/23

If I configure the port to be access port, if is disabled by spanning tree.

The only way to get a green link on port Fas 0/23 is if I configure the port as a Trunk, but then I get the above error.

The 2950 is the VTP server and the Root Bridge for Spanning-Tree, but the port shows bloked. I've tried changing the native VLANs but no luck.

The switch has more VLANs, and I have a 2800 router that I want to connect.

I'm stucked from help!

I will really appreciate some help!

Federico.

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Port error on Switch 2950

Federico

Glad it worked. You can have your spanning-tree ON without any issues now... on 2950's unfortunately you cant have your spanning tree disabled per port.. you need to have it disabled on the vlan. other way is to convert the port to layer 3 (avoiding layer 2), but thats not possible with 2950 since it is a layer 2 switch.. do let us know if you face any other issues..

Raj

10 REPLIES

Re: Port error on Switch 2950

Hi Federico

Can you please post us the configs in Fas 0/23 ? What is connected on Fas 0/22 ?? Spanning tree is blocking this port for some reason, and we would like to know the configs and network architecture more in detail, to see whats the issue...

Raj

Re: Port error on Switch 2950

On port Fas 0/22 i have the computer connected.

On port Fas 0/23 i have the CPE connected.

Here's the part of the config for both ports:

!
interface FastEthernet0/22
switchport mode access
!
interface FastEthernet0/23
description LINK_ADSL
switchport mode trunk

IT_2950#
IT_2950#sh int trun

Port        Mode         Encapsulation  Status        Native vlan
Fa0/5       on           802.1q         trunking      1
Fa0/6       on           802.1q         trunking      1
Fa0/23      on           802.1q         trunking      1

Port      Vlans allowed on trunk
Fa0/5       11-12
Fa0/6       11-12
Fa0/23      1-4094

Port        Vlans allowed and active in management domain
Fa0/5       11-12
Fa0/6       11-12
Fa0/23      1,5,11-12,14-17,19-20,29,40,100-101

Port        Vlans in spanning tree forwarding state and not pruned
Fa0/5       11-12
Fa0/6       11-12
Fa0/23      5,11-12,14-17,19-20,29,40,100-101

IT_2950#sh spanning-tree vlan 1

VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32769
             Address     0015.2b7e.2d80
             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     0015.2b7e.2d80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/22           Desg FWD 19        128.22   P2p
Fa0/23           Desg BKN*19        128.23   P2p *PVID_Inc

I don't understand why VLAN 1 does not show under port Fast 0/23 for the Vlans in spanning tree forwarding state and not pruned.

I've also tried putting port Fast 0/22 in a another VLAN.

If I put Fast 0/23 in Access Mode (my first intention), I get a spanning-tree inconsistent error and only a orange light on the port.

Re: Port error on Switch 2950

PVID_Inc - shows that the port is blocked due to Port VLAN ID inconsistency...

this could happen because of 2 reasons:

1) native vlan mismatch between the switch and router - i see there is no native vlan configured, so it defaults to zero...

2) switch side you have dot1q trunk configured, but what is configured on CPE side ? what is the device you have in CPE ? you need to have trunk configured on the CPE to avoid this error.. Do you have sub-interfaces configured on CPE for all vlans to be routed ?

Go through this doc, and it gives more info on wht you need to look at:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml

Hope this helps.. all the best..

Raj

Re: Port error on Switch 2950

Thank you.

The problem is that if I connect the computer directly to the CPE it works fine.

I assumed i just needed to create a VLAN and put the port that connects to the CPE and to the Router (or computer) on the same VLAN.

But why when I put the Fast 0/23 (connects to CPE) as access port I get an Spanning Tree inconsistent error. Then I put it in Trunk Mode, but i get it blocked by Spanning Tree eventhough the Switch 2950 is the Root Bridge!

The Service Provider is giving me no help.

The problem is definitely the connection between the CPE and the port Fast 0/23 on the Switch, but I get inconsistent error if in access mode, and blocked in Trunk Mode.

All the provider says is that the port on the CPE is an IP port, and they don't use VLANs to communicate with use. That's why I was using just the same VLAN on both ports at first.

Any other thorughts?

Federico.

Re: Port error on Switch 2950

Hi Fredrico

SInce you arent sure of what is running on the CPE, we wouldnt have much info to troubleshoot this issue.. If you are sure that this is the only place of exit, and is a layer 3 port, you can probably disable spanning tree on this uplink port, to check if it solves your issue.. again, only if you know what kind of connectivity is there between your switch and the CPE !!! incase this was a Layer3 switch we would have had more options of configuring L3 P2P between the switch and CPE, but unfortunaltey 2950's are Layer 2 ....

Hope this helps..

Raj

Re: Port error on Switch 2950

Let me try that!

How do I disable Spanning Tree only on Port Fast 0/23 ??

The 2950 is running "flash:/c2950-i6q4l2-mz.121-22.EA4.bin"

Thanks!

Re: Port error on Switch 2950

I see the problem now.

I am getting this errors, when I change from VLAN 1 to VLAN 40:

00:14:26: %SYS-5-CONFIG_I: Configured from console by console
00:31:42: %SYS-5-CONFIG_I: Configured from console by vty0 (192.168.1.27)
00:35:11: %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0/23 VLAN40.
00:35:11: %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0/23 on VLAN0040. Inconsistent port type.
00:35:11: %SYS-5-CONFIG_I: Configured from console by vty0 (192.168.1.27)
00:36:37: %SPANTREE-7-RECV_1Q_NON_TRUNK: Received 802.1Q BPDU on non trunk FastEthernet0/23 VLAN1.
00:36:37: %SPANTREE-7-BLOCK_PORT_TYPE: Blocking FastEthernet0/23 on VLAN0001. Inconsistent port type.
00:36:42: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to down
00:36:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to up
00:36:49: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 3054 on FastEthernet0/23 VLAN1.
00:36:49: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking FastEthernet0/23 on VLAN0001. Inconsistent local vlan.

So, i assume the port on the CPE is a trunk port, and the native VLAN, or the VLAN I should use if the VLAN 3054.

The problem is that I don't see how to enable VLAN 3054 on this 2950....  only up to VLAN 1001

Is there a way to configure up to 4096 VLANs on this Switch??????  Maybe that solves the problem.

Re: Port error on Switch 2950

Hi fredrico

2950's with Standard Image supports only 64 VLANs, and EI supports 250 VLANs.. Anyways with regards to VLAN numbering, VLANs are identified with 1-4094 when Enhanced Image is running on your switch. With standard Image you will see 1-1005.. i saw a command before which allowed vlans 1-4094 on your trunk, and hence your switch should support vlan numbers greater than 1005.. what version of IOS are you running ? Is it EI or SI ? WHat is the VTP mode on your switch ? In CCO it says that your switch must be in transparent mode, when you create VLAN IDs from 1006 to 4094 !!

Regards

Raj

Re: Port error on Switch 2950

Done!

I fixed the problem.

I added the switch as a transparent VTP, enable extended VLANs, and configure VLAN 3054 as the native VLAN.

I got a consistent message now, and Internet access!!!

Re: Port error on Switch 2950

Federico

Glad it worked. You can have your spanning-tree ON without any issues now... on 2950's unfortunately you cant have your spanning tree disabled per port.. you need to have it disabled on the vlan. other way is to convert the port to layer 3 (avoiding layer 2), but thats not possible with 2950 since it is a layer 2 switch.. do let us know if you face any other issues..

Raj

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