[Troubleshooting Series] Case 51 MSTP is configured, then the interface fails to be forwarded by BLOCK

Created: Feb 11, 2019 09:14:32 542 0 0 1


Physical Network Topology

If four devices are configured with VLAN 100 and VLAN 300 on the four devices, then configure MSTP instances for VLAN 100 and VLAN 300, and then configure the vrrp gateway on the CE6851-1 and CE6851-2 devices. Found that the VRRP gateway has a dual master problem.

Figure 1-1 MSTP is configured, then the interface fails to be forwarded by BLOCK

090734dyz8p6gl797bg4ke.png

 

Fault Description

The vrrp status on the CE6851-1 device
===========================================================================
display vrrp verbose
===========================================================================
Vlanif100 | Virtual Router 1
State          : Master
Virtual IP     : 10.1.1.111
Master IP      : 10.1.1.1
PriorityRun    : 120
PriorityConfig : 120
MasterPriority : 120
Preempt        : YES   Delay Time : 20s   Remain : --
Hold Multiplier: 3
TimerRun       : 1s
TimerConfig    : 1s
Auth Type      : NONE
Virtual MAC    : 0000-5e00-0101
Check TTL      : YES
Config Type    : Normal
Create Time       : 2018-09-03 01:28
Last Change Time  : 2018-09-03 01:28
The vrrp status on the CE6851-2 device

===========================================================================
display vrrp verbose
===========================================================================
Vlanif100 | Virtual Router 1
State          : Master
Virtual IP     : 10.1.1.111
Master IP      : 10.1.1.2
PriorityRun    : 100
PriorityConfig : 100
MasterPriority : 100
Preempt        : YES   Delay Time : 0s   Remain : --
Hold Multiplier: 3
TimerRun       : 1s
TimerConfig    : 1s
Auth Type      : NONE
Virtual MAC    : 0000-5e00-0101
Check TTL      : YES
Config Type    : Normal
Create Time       : 2018-09-03 01:28
Last Change Time  : 2018-09-03 01:28

Configuration Files

l   CE6851_4

#
vlan batch 300
#
stp region-configuration
 instance 1 vlan 100
 instance 2 vlan 300
#
interface Vlanif300
 ip address 192.168.1.4 255.255.255.0
#
interface MEth0/0/0
 ip address 10.9.162.40 255.255.255.0
#
interface 10GE1/0/11
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 300
 device transceiver 10GBASE-COPPER
#
interface 10GE1/0/12
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 300
 device transceiver 10GBASE-COPPER
#
ip route-static 10.9.0.0 255.255.0.0 10.9.162.253
#

l   CE6851_3

#
vlan batch 100 300
#
stp region-configuration
 instance 1 vlan 100
 instance 2 vlan 300
#
interface Vlanif100
 ip address 10.1.1.3 255.255.255.0
#
interface MEth0/0/0
 ip address 10.9.162.30 255.255.255.0
#
interface 10GE1/0/1
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 100
 device transceiver 10GBASE-COPPER
#
interface 10GE1/0/2
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 100
 device transceiver 10GBASE-COPPER
#
ip route-static 10.9.0.0 255.255.0.0 10.9.162.253

l   CE6851_2

#
vlan batch 100 300
#
stp region-configuration
 instance 1 vlan 100
 instance 2 vlan 300
#
interface Vlanif100
 ip address 10.1.1.2 255.255.255.0
 vrrp vrid 1 virtual-ip 10.1.1.111
#
interface Vlanif300
 ip address 192.168.1.2 255.255.255.0
 vrrp vrid 2 virtual-ip 192.168.1.111
#
interface MEth0/0/0
 ip address 10.9.162.20 255.255.255.0
#
interface 10GE1/0/2
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 100
 device transceiver 10GBASE-COPPER
#
interface 10GE1/0/12
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 300
 device transceiver 10GBASE-COPPER
#
interface 10GE1/0/20
 shutdown
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 100
 device transceiver 10GBASE-COPPER
#
ip route-static 10.9.0.0 255.255.0.0 10.9.162.253

l   CE6851_1

#
vlan batch 100 300
#
stp region-configuration
 instance 1 vlan 100
 instance 2 vlan 300
#
interface Vlanif100
 ip address 10.1.1.1 255.255.255.0
 vrrp vrid 1 virtual-ip 10.1.1.111
 vrrp vrid 1 priority 120
 vrrp vrid 1 preempt timer delay 20
#
interface Vlanif300
 ip address 192.168.1.1 255.255.255.0
 vrrp vrid 2 virtual-ip 192.168.1.111
 vrrp vrid 2 priority 120
 vrrp vrid 2 preempt timer delay 20
#
interface MEth0/0/0
 ip address 10.9.162.100 255.255.255.0
#
interface 10GE1/0/2
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 100
 device transceiver 10GBASE-COPPER
#
interface 10GE1/0/12
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 300
 device transceiver 10GBASE-COPPER
#
interface 10GE1/0/20
 port link-type trunk
 undo port trunk allow-pass vlan 1
 port trunk allow-pass vlan 100
 device transceiver 10GBASE-COPPER
#
ospf 1
 area 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 192.168.1.0 0.0.0.255
#
ip route-static 10.9.0.0 255.255.0.0 10.9.162.253

Troubleshooting Procedure

                               Step 1      The status of the VRRP device is displayed. The status of the VRRP device is displayed. The status of the interface is as follows:

==============================================================================
display stp brief
==============================================================================
MSTID  Port                        Role  STP State     Protection      Cost    Edged
0  10GE1/0/1                   ROOT  forwarding    none            2000    disable
0  10GE1/0/2                   ALTE  discarding    none            2000    disable
1  10GE1/0/1                   MAST  forwarding    none            2000    disable
1  10GE1/0/2                   ALTE  discarding    none            2000    disable

                               Step 2      Check the STP status of the three devices and find that the STP instance root of the instance 1 of the VLAN learns the CE6851-4 device. The detailed information is as follows:

==============================================================================
display stp
==============================================================================
CIST Global Information:
Mode                :MSTP
CIST Bridge         :32768.48fd-8e02-c751
Config Times        :Hello 2s MaxAge 20s FwDly 15s MaxHop 20
Active Times        :Hello 2s MaxAge 20s FwDly 15s MaxHop 20
CIST Root/ERPC      :32768.48fd-8e02-c6f1 / 4000  // The MAC address is the MAC address of the CE6851-4 device.
CIST RegRoot/IRPC   :32768.48fd-8e02-c751 / 0 (This bridge is the root)
CIST RootPortId     :128.2 (10GE1/0/1)
BPDU-Protection     :Disabled
TC or TCN received  :52
TC count per hello  :0
STP Converge Mode   :Normal
Share region-configuration :Enabled
Time since last TC  :0 days 0h:38m:31s
Number of TC        :10
Last TC occurred    :10GE1/0/1
Topo Change Flag    :0

                               Step 3      After the device is configured in the same MSTP domain, the VRRP status of the CE685101 and CE6851-2 devices can be changed to active or standby. The detailed information is as follows:

===========================================================================
display vrrp verbose
===========================================================================
Vlanif100 | Virtual Router 1
State          : Master
Virtual IP     : 10.1.1.111
Master IP      : 10.1.1.1
PriorityRun    : 120
PriorityConfig : 120
MasterPriority : 120
Preempt        : YES   Delay Time : 20s   Remain : --
Hold Multiplier: 3
TimerRun       : 1s
TimerConfig    : 1s
Auth Type      : NONE
Virtual MAC    : 0000-5e00-0101
Check TTL      : YES
Config Type    : Normal
Create Time       : 2018-09-03 01:28
Last Change Time  : 2018-09-03 01:28

                               Step 4      On the device CE6851-2 device:

===========================================================================
display vrrp On the device CE6851-2 device:ose
===========================================================================
Vlanif100 | Virtual Router 1
State          : Backup
Virtual IP     : 10.1.1.111
Master IP      : 10.1.1.2
PriorityRun    : 100
PriorityConfig : 100
MasterPriority : 100
Preempt        : YES   Delay Time : 0s   Remain : --
Hold Multiplier: 3
TimerRun       : 1s
TimerConfig    : 1s
Auth Type      : NONE
Virtual MAC    : 0000-5e00-0101
Check TTL      : YES
Config Type    : Normal
Create Time       : 2018-09-03 01:28
Last Change Time  : 2018-09-03 01:28

Root Cause

The devices CE6851-1, CE6851-2, and CE6951-3 are not configured in an MSTP domain. MSTP1-4 calculates the CE6851-4 device as the root of the MSTP. The device does not have VLAN 100. This causes CE6851. The interface above the -3 device is blocked.

 


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