01-09-2013 08:33 AM - edited 03-07-2019 11:00 AM
Hello!
We have a large L2 network with one MSTI region and few ring topologies.
The topology looks like this:
Rings-swA-\ / ---Ring10G (l2 cloud)-- \
\ / \
\ [Te1/29] \
sw-Core [Te1/30] --- swC--- SW-ROOT
/ \ /
Rings-swB-/ \ ----- Ring 1G (l2 cloud)--- /
It all started after the closure 10G ring.
In general periodically from all sides sw-Core sees 'BPDU received 0'.
Neighbors in the 0-th (CST) instance sees the packages, but in the 1-st (operating) no.
After that they put the ports into position 'blk disput'.
It is understandable, because sw-core does not see BPDU from them, so it
can not answer.
Why it does not sees BPDU from neighbors? - a mystery.
Increasing TTL up to 40 - have no result. Treated only reboot of switch.
IOS: cat4500-entservicesk9-mz.122-54.SG.bin
Here is configuration of MSTP
spanning-tree mode mst
spanning-tree logging
spanning-tree extend system-id
!
spanning-tree mst configuration
instance 1 vlan 1-4094
show spanning-tree mst
##### MST0 vlans mapped: none
Bridge address 0022.55e9.f7c0 priority 32768 (32768 sysid 0)
Root address 5057.a8ab.1380 priority 8192 (8192 sysid 0)
port Te1/30 path cost 0
Regional Root address 5057.a8ab.1380 priority 8192 (8192 sysid 0)
internal cost 2000 rem hops 19
Operational hello time 2 , forward delay 15, max age 20, txholdcount 6
Configured hello time 2 , forward delay 15, max age 20, max hops 20
show spanning-tree mst
##### MST0 vlans mapped: none
Bridge address 0022.55e9.f7c0 priority 32768 (32768 sysid 0)
Root address 5057.a8ab.1380 priority 8192 (8192 sysid 0)
port Te1/30 path cost 0
Regional Root address 5057.a8ab.1380 priority 8192 (8192 sysid 0)
internal cost 2000 rem hops 19
Operational hello time 2 , forward delay 15, max age 20, txholdcount 6
Configured hello time 2 , forward delay 15, max age 20, max hops 20
============================================================
show spanning-tree mst interface TenGigabitEthernet1/30
TenGigabitEthernet1/30 of MST0 is root forwarding
Edge port: no (default) port guard : none (default)
Link type: point-to-point (auto) bpdu filter: disable (default)
Boundary : internal bpdu guard : disable (default)
Bpdus sent 20, received 90131
Instance Role Sts Cost Prio.Nbr Vlans mapped
-------- ---- --- --------- -------- -------------------------------
0 Root FWD 2000 128.30 none
1 Root FWD 2000 128.30 1-4094
============================================================
show spanning-tree mst interface TenGigabitEthernet1/29
TenGigabitEthernet1/29 of MST0 is designated forwarding
Edge port: no (default) port guard : none (default)
Link type: point-to-point (auto) bpdu filter: disable (default)
Boundary : internal bpdu guard : disable (default)
Bpdus sent 89815, received 5
Instance Role Sts Cost Prio.Nbr Vlans mapped
-------- ---- --- --------- -------- -------------------------------
0 Desg FWD 2000 128.29 none
1 Desg FWD 2000 128.29 1-4094
01-09-2013 08:46 AM
Hello,
You might want to configure VLAN 1 in MST0 to exchange bpdus
Rgds.
01-10-2013 08:24 AM
Thanks for you response.
As I know MSTP does not send MSTI’s information in separate BPDUs, this information is piggybacked into the IST’s BPDUs using special M-Record fields.
So, I can have multiple MSTI or one with whole vlan range (1-4096) no matter.
In any case, BPDU will be propagated in MST0 (Internal Spanning Tree) and will consist of such components as configuration name, revision number and a hash value calculated over VLANs to MSTI mapping table contents
I think that this problem may apear due very large L2 segment. So value "Max Hops" exhausts itself in some cases.
As a result sw-core receives BPDU 0 and after that happens the following scenario
sw-Core ceases to receive BPDU from all neighbors and and decides that he is root.
Upstream switches sends superior root bridge information to the sw-Core bridge but receives the BPDUs with Designated bit set, the upstream switch concludes that the downstream does not hear its BPDU’s. The upstream switch then blocks the downstream port and marks it as STP dispute link
BUT Why sw-CORE ceases to receive BPDU from ALL neighbors? - a mystery.
01-10-2013 09:33 AM
Hello Andrey,
I wonder - how many switches are connected in single ring? You also indicated that you increased "TTL" - you probably mean the STP max-hops parameter, right? What command did you use for that? Can you also confirm that none of the ports on the ring is described as a boundary port? We want to make sure that the ring is not inadvertently split into several regions.
Best regards,
Peter
01-11-2013 04:26 AM
We have eight switches in 1G ring and nine in 10G ring.
1G Ring ends on another switch not on sw-Core
You also indicated that you increased "TTL" - you probably mean the STP max-hops parameter, right?
Yes you are right. The command which we used was "spanning-tree mst max-hops"
Here Is a state of ports
Gi1/1 Desg FWD 20000 128.1 P2p Edge
Gi1/2 Desg FWD 20000 128.2 P2p Edge
Gi1/3 Desg FWD 20000 128.3 P2p Edge
Gi1/4 Desg FWD 20000 128.4 P2p Edge
Gi1/5 Desg FWD 20000 128.5 P2p Edge
Gi1/6 Desg FWD 20000 128.6 P2p Edge
Gi1/7 Desg FWD 20000 128.7 P2p Edge
Gi1/8 Desg FWD 20000 128.8 P2p Edge
Gi1/9 Desg FWD 20000 128.9 P2p Edge
Gi1/10 Desg FWD 20000 128.10 P2p Edge
Gi1/11 Desg FWD 20000 128.11 P2p Edge
Gi1/12 Desg FWD 20000 128.12 P2p Edge
Gi1/13 Desg FWD 20000 128.13 P2p Edge
Gi1/14 Desg FWD 20000 128.14 P2p Edge
Gi1/15 Desg FWD 20000 128.15 P2p Edge
Gi1/16 Desg FWD 20000 128.16 P2p Edge
Gi1/17 Desg FWD 20000 128.17 P2p Edge
Gi1/18 Desg FWD 20000 128.18 P2p Edge
Gi1/21 Desg FWD 20000 128.21 P2p Edge
Gi1/22 Desg FWD 20000 128.22 P2p Edge
Gi1/23 Desg FWD 20000 128.23 P2p // 1G RING port
Gi1/24 Desg FWD 20000 128.24 P2p Edge
Gi1/26 Desg FWD 20000 128.26 P2p Edge
Te1/29 Desg FWD 2000 128.29 P2p // 10G ring port
Te1/30 Root FWD 2000 128.30 P2p // 10G ring port
> Interface Role Sts Cost Prio.Nbr Type
> ---------------- ---- --- --------- --------
> --------------------------------
> Gi1/1 Desg FWD 20000 128.1 P2p Edge
> Gi1/2 Desg FWD 20000 128.2 P2p Edge
> Gi1/3 Desg FWD 20000 128.3 P2p Edge
> Gi1/4 Desg FWD 20000 128.4 P2p Edge
> Gi1/5 Desg FWD 20000 128.5 P2p Edge
> Gi1/6 Desg FWD 20000 128.6 P2p Edge
> Gi1/7 Desg FWD 20000 128.7 P2p Edge
> Gi1/8 Desg FWD 20000 128.8 P2p Edge
> Gi1/9 Desg FWD 20000 128.9 P2p Edge
> Gi1/10 Desg FWD 20000 128.10 P2p Edge
> Gi1/11 Desg FWD 20000 128.11 P2p Edge
> Gi1/12 Desg FWD 20000 128.12 P2p Edge
> Gi1/13 Desg FWD 20000 128.13 P2p Edge
> Gi1/14 Desg FWD 20000 128.14 P2p Edge
> Gi1/15 Desg FWD 20000 128.15 P2p Edge
> Gi1/16 Desg FWD 20000 128.16 P2p Edge
> Gi1/17 Desg FWD 20000 128.17 P2p Edge
> Gi1/18 Desg FWD 20000 128.18 P2p Edge
> Gi1/21 Desg FWD 20000 128.21 P2p Edge
> Gi1/22 Desg FWD 20000 128.22 P2p Edge
> Gi1/23 Desg FWD 20000 128.23 P2p
> Gi1/24 Desg FWD 20000 128.24 P2p Edge
> Gi1/26 Desg FWD 20000 128.26 P2p Edge
> Te1/29 Desg FWD 2000 128.29 P2p
> Te1/30 Root FWD 2000 128.30 P2p
01-11-2013 05:33 AM
Hello Andrey,
Thank you for the additional information. Let me ask you - in the current state, does the MSTP behave correctly, or do you still experience problems? You have mentioned something related to a reboot but I did not understand what you wanted to say.
Also, please try to post the exact show command output you consider to be abnormal. I admit I am still struggling to understand what exact problems are you experiencing.
Thank you!
Best regards,
Peter
01-14-2013 08:48 AM
Hello!
I am confident that we found the problem.
The problem consisted of several mistakes
First of all, because we did not implemented the third version of the VTP on time
And then was an administrative mistake. It turned out that we had forgotten about the old switch, which was a server in the same VTP domain as the sw-core. Despite the fact that options "no vtp" have been enabled, but this option works only with VTP ver. 3. So, when we had some changes on old switch, then sw-core received higher vtp revision and switched to client mode. After that all neighbors worked with sw-core on STP, because vlan database was not match for MSTP participant and not correctly mapped to MSTI.
All for the same reason that vtp version was number 2.
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