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
