Configuring M-LAG Consistency Check
Prerequisites
The DFS group between two devices in the M-LAG has been paired successfully and the master and backup states have been negotiated.
Context
- Key configuration (Type 1): If the configurations of two devices in the M-LAG are inconsistent, problems may occur, for example, loops may occur or packets are discarded for a long period of time though the M-LAG status is normal.
In strict mode, if the key configuration of two devices in the M-LAG is inconsistent, member interfaces on the M-LAG backup device enter the Error-Down state and the alarm about key configuration inconsistency is generated.
In loose mode, if the key configuration of two devices in the M-LAG is inconsistent, the alarm about key and common configuration inconsistency is generated.
- Common configuration (Type 2): If the configurations of two devices in the M-LAG are inconsistent, the M-LAG status may be abnormal. Compared with the key configuration, the common configuration problem can be easily detected and has less impact on the live network.
Regardless of the mode, if the following common configuration of two devices in the M-LAG is inconsistent, the alarm about key and common configuration inconsistency is generated.
View |
Configuration |
Type |
|---|---|---|
System view |
Whether STP is enabled |
Type 1 |
STP working mode |
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Whether BPDU protection is enabled |
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Mapping between VLANs and MSTIs NOTE:
The device checks the mapping between VLANs and MSTIs in STP process 0. |
||
M-LAG member interface view |
Whether STP is enabled |
|
Whether root protection is enabled |
||
LACP mode |
||
System view |
VLAN configuration |
Type 2 |
Static MAC address entries
|
||
Aging time of dynamic MAC address entries |
||
Static ARP entries
NOTE:
The switch cannot check short static ARP entries of a specified VPN instance. If the outbound interface of a long static ARP entry is an M-LAG member interface and is bound to a VPN instance or the VLANIF interface corresponding to the VLAN to which the outbound interface belongs is bound to a VPN instance, the switch cannot check the static ARP entry. |
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Aging time of dynamic ARP entries |
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Bridge Domain (BD) configuration
|
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VBDIF interface configuration
NOTE:
The device only checks the virtual MAC address by default. For the IPv6 address and VRRP4 configuration, the consistency check only take effect when the VBDIF interface is up. If the VBDIF interface is down, the preceding configurations do not take effect on the interface. |
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VLANIF interface configuration
NOTE:
The device only checks the virtual MAC address by default. For the IPv6 address and VRRP4 configuration, the consistency check only take effect when the VLANIF interface is up. If the VLANIF interface is down, the preceding configurations do not take effect on the interface. |
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M-LAG member interface view |
STP priority |
|
VLAN ID |
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Parameters |
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Number of member interfaces of the Eth-Trunk to which an M-LAG member interface belongs
NOTE:
Only the numbers of member interfaces of Eth-Trunks are compared. The physical Up/Down status or bandwidth of member interfaces is not checked. |
Procedure
- Configure M-LAG consistency check.
- Check the M-LAG consistency check status and configuration of devices in the M-LAG.
- Run the display dfs-group command to check the M-LAG consistency check result.
- Run the display dfs-group consistency-check { global | interface m-lag m-lag-id | static-arp | static-mac } command to check the configuration of M-LAG master and backup devices.
- Run the display dfs-group consistency-check status command to display the running status of M-LAG consistency check.
Exception Handling
- In loose mode, if the key or common configuration of two devices in the M-LAG is inconsistent, either of the following alarms is triggered: "ETRUNK_1.3.6.1.4.1.2011.5.25.178.8.2.1 hwMLagConsistencyCheckType1" and "ETRUNK_1.3.6.1.4.1.2011.5.25.178.8.2.3 hwMLagConsistencyCheckType2".
When the configuration of two devices in the M-LAG is adjusted, M-LAG consistency check is successful and the alarm is cleared.
- In strict mode, if the key configuration of two devices in the M-LAG is inconsistent, member interfaces on the M-LAG backup device enter the Error-Down state and the alarm about key configuration inconsistency is generated: "ETRUNK_1.3.6.1.4.1.2011.5.25.178.8.2.1 hwMLagConsistencyCheckType1".
The device records the status of an interface as Error-Down when it detects that a fault occurs. The interface in Error-Down state cannot receive or send packets and the interface indicator is off. You can run the display error-down recovery command to check information about all interfaces in Error-Down state on the device.
When the interface enters the Error-Down state, adjust the configuration of M-LAG master and backup devices. You are not advised to manually restore the interface or run the error-down auto-recovery cause m-lag interval interval-value command in the system view to enable the interface to go Up automatically. Otherwise, excess packets, packet loss, or forwarding failure may occur. Exercise caution when you perform the preceding operation.
If the M-LAG consistency check mode is set to strict mode and the system detects that type 1 configurations of the two M-LAG devices are inconsistent, it is recommended that the device administrator immediately adjust the configurations, and it is not recommended that the device administrator restart the devices. If type 1 configurations are inconsistent, member interfaces on the M-LAG backup device enter the Error-Down state and the alarm about type 1 configuration inconsistency is generated.
If the administrator does not adjust the configurations and restarts the M-LAG master device, interfaces on the M-LAG backup device may enter the Error-Down state because of type 1 configuration inconsistency during re-negotiation between M-LAG devices when the master device is recovering. In this case, M-LAG member interfaces on the M-LAG master device go Up after a delay. As a result, both the M-LAG master and backup devices fail to forward traffic, and services are interrupted.