ā09-07-2011 09:44 AM
Hello,
I have a problem of configuration of STP on my switches.
The central switch is peered with two ME-3800X .
I have imposed the " l2protocol forward" on interface of 3800X, but i have an error on the central switch:
- STP dispute on interface Gi 0/25
- The interface 0/27 is STP forward state.
No loop, the interface 0/25 is blocked , dispute.
See the diagram .pdf please.
Help me !
AndrƩ.
Solved! Go to Solution.
ā10-13-2011 01:32 AM
Yes, seems like same bug i had told you before.
ā09-08-2011 06:17 AM
Hi Andre',
STP dispute occurs when a switch detetcts that a neighbor switch does not react to superior BPDU's sent by it and keeps on sending inferior BPDU's on that link with designated role and learning bit on.
In order to avoid possible loops (the assumption is that the link to the neighbor switch is unidirectional) the switch puts that port in blocking state - dispute. This is the theory.
About your case I suppose that the central switch is supposdely the root bridge, or it should be, correct?
About the BPDU's handling from Me3800x perspective, what those switches should do, process the bpdu's locally or forward (tunnel) them?
According to the syntax you are using a post 15.1(2)EY IOS release as the 'l2protocol forward' command has been added from this image onwards (before only peer and tunnel options were available) to overcome and interoperability issue between 7600 and me3800x.
To make a long story short there is still some confusion (even in Cisco documentation) about the 3 options for the l2protocol command. The exact behaviors are not properly documented anywhere but they should be:
l2protocol peer: PDUs are processed locally
l2protocol tunnel: Overwrites the PDU-destination MAC address with a well-known Cisco proprietary multicast address (01-00-0c-cd-cd-d0)
l2protocol forward: forwards the PDU without any change or local processing (like the 7600 behavior) with multicast address 01-00-0c-cc-cc-cd.
By configuring l2protocol forward cdp you are instructing the switch to tunnel cdp but not specific intructions is given for STP BPDUs (and to be honest with you I don't know what the default behavior should be at this stage).
So, the question I asked before is coming back. What the ME3800x is supposed to do with those BPDUs?
Can you try to configure the correct l2protocol command matching the behavior you wish for BPDUs?
regards,
Riccardo
ā09-08-2011 06:55 AM
little addendum in case you still have the issue even though you change the l2protocol command.
If this is the case we need to know who is the root for MST and what is the MST status on the central switch and the 2 me3800x
for that we need from the 3 switches
show spanning
show spanning mst
and then
on central switch 3 times with a second interval (I would like to see BPDUs sent/received counters increasing).
show spann mst inter gi0/25
show spann mst inter gi0/27
on the 2x me3800x
show spann mst inter gi0/1 serv inst 1 (again 3 times with 1 second interval)
ā09-08-2011 07:17 AM
Hello,
About your case I suppose that the central switch is supposdely the root bridge, or it should be, correct?
>>Yes
About the BPDU's handling from Me3800x perspective, what those switches should do, process the bpdu's locally or forward (tunnel) them?
>> Forward
Can you try to configure the correct l2protocol command matching the behavior you wish for BPDUs?
Yes , it is done.
I have a probleme, it is not possible !!
If I connect the switches on one ME-3800-X on two interfcace on same bridge-domaine > It is OK.
But on different ME-3800-X with l2protocol forward > it is not good.
************************************************************
on switch central
switch_A#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
switch_A#
*********************
ā09-08-2011 07:20 AM
I post the show command as soon as possible.
Thanks,
ā09-08-2011 07:23 AM
ok
but beside the outputs I see from your confiuration that you have 'l2protocol forward cdp'. I don't see stp instead.
Can you try 'l2protocol forward stp' and if it does not work 'l2protocol tunnel stp' instead?
Riccardo
ā09-08-2011 07:31 AM
but beside the outputs I see from your confiuration that you have 'l2protocol forward cdp'. I don't see stp instead.
>> I have tested CDP for see if "protocol forward" is ok. but...
Can you try 'l2protocol forward stp' and if it does not work 'l2protocol tunnel stp' instead?
I have tested both cdp an STP, but no ok.
Cdlt,
ā09-08-2011 10:27 AM
AndrĆØ, at this stage I need to see the stp outputs.
Also, are you completely sure that you don't want the me3800x to process/partecipate in stp? if this is the case I expect to see an equivalent forward/tunnel command on the evc towards the rest of the ring. Do you have it.
Have you tried 'l2protocol peer stp' instead?
Please attach a complet config of the metro boxes indicating what is the interface connected to the ring.
ā09-08-2011 11:04 AM
Riccardo,
Excuse me for my bad english !
The ME-3800-X does not participate at spannig-tree, it's "provider".
It must be transparent at BPDUs and CDP packet of client site.
Tomorrow; i would give the configuration of ME-3800-X and best diagram of network.
Good night,
ā09-08-2011 11:15 AM
Riccardo,
In release note:
There is a Bug :
****
CSCtr63989
L2PT forward broken over VPLS
******
ā09-09-2011 05:19 AM
Andre',
that bug is pretty vague and criptic (also its internal notes are).
Apparently it says that the issue occurs only if forward key is used while with the tunnel key there is no problem. In your case it seems that nothing gets tunneled either ways.
Honestly I don't know if it is a match... deeper troubleshooting is needed.
You'd better open a TAC case and have somebody closely check your network and investigate around that bug too.
If you open it during EMEA hours you can tell the TAC engineer to contact me for background info.
Riccardo
ā09-09-2011 10:59 PM
Hello Riccardo,
After some tests :
- L2 forward protocol CDP STP on PW EoMPS is OK !!
But it is point to point.....
But not on VPLS.
I think my configuration is good. It is not complicated.
But not on VPLS.
I have open a Case via my partner Cisco.
The partner has vƩrified my configuration.
ā09-15-2011 02:41 AM
Hi Andre',
sorry I have been pretty busy lately.
What is the outcome of the TAC case?
Riccardo
ā09-15-2011 03:03 AM
Hi Riccardo,
I have not of outcome of my case.
Cordialy,
ā10-11-2011 04:38 AM
Hi Riccardo,
It is a bug !
After a reload , it works.
After a configuration from scratch, it works.
When i modify the configuration in real time,I have a problem.
I would tell you what happens
Cordialy,
AndrƩ
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