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The MAC Addresses of VLANs Are Improperly Learned Due to the NE40E That Supports the Learning of MAC Addresses Only in Unqualified Mode

Publication Date:  2012-07-27 Views:  51 Downloads:  1
Issue Description
For the networking, see the appendix.
Symptom of the fault: The VPLS is established between the NE40E and the MA5200Gs. In the same VPLS instance, adjacency is created between the NE40E and multiple MA5200Gs. After that, the S8505 cannot learn the MAC addresses of VLANs normally. Generally, the MAC addresses are learned by downlink ports. But in this case, the MAC addresses are learned by uplink ports.
The configuration of the VPLS established on the NE40E is as follows:
vsi dianyuanjiankong static
pwsignal ldp
vsi-id 123
peer 218.75.128.207
peer 218.75.128.219
peer 218.75.128.221
peer 218.75.128.220
The following operations are then performed: Create multiple instances so that one NE40E maps one MA5200G. Then the fault disappears.
vsi lxdyjk static
pwsignal ldp
vsi-id 219
peer 218.75.128.219
#
vsi smdyjk static
pwsignal ldp
vsi-id 207
peer 218.75.128.207
#
vsi jsdyjk static
pwsignal ldp
vsi-id 221
peer 218.75.128.221
#
vsi axdyjk static
pwsignal ldp
vsi-id 220
peer 218.75.128.220 
 
Alarm Information
When the fault occurs, the S8505 learns the MAC addresses of VLANs through uplink ports and the MAC addresses keep drifting between uplink and downlink ports. The services are thus affected. 
Handling Process
1. Check whether loops exist on Layer 2 devices and capture packets for analysis when the fault occurs. It is found that the fault is not caused by loops.
2. Because the fault occurs when adjacency is established between one NE40E and multiple MA5200Gs in one VPLS instance, it is suspected that the VPLS implementation mechanism of the NE40E is the cause of the fault.
3. The NE40E learns VPLS MAC addresses as follows:
In the VPLS, the PSN simulates the network bridge. The PE learns MAC addresses. To forward packets, the PE must be able to associate destination MAC addresses with PWs. The PE learns remote MAC addresses through PWs and learns MAC addresses of devices directly connected through ACs.
MAC addresses can be learned in the following modes:
Qualified: The PE learns MAC addresses based on the MAC addresses and VLAN tag in Ethernet packets, that is, based on each VLAN of each VSI. In this mode, each VLAN forms its own broadcast domain and has independent MAC address space.
Unqualified: The PE learns MAC addresses based on the MAC addresses in Ethernet packets, that is, based on each VSI. In this mode, all VLANs share a broadcast domain and the MAC address space. The MAC address of a VLAN must be unique and cannot be the same as the MAC address of another VLAN.
Currently, the NE80E and NE40E support the learning of MAC addresses only in unqualified mode. In other words, the MAC address of a VLAN must be unique. In the preceding networking, in one VPLS instance, the MAC addresses of VLAN 85 and VLAN 86 learned are both the MAC address of the gateway on the S6506. Thus, the MAC address drifts between downlink and uplink ports.
4. Modify the VPLS configuration. On the NE40E, one-to-one adjacency is established between NE40Es and MA5200Gs in each VPLS instance. This ensures that each VLAN has a unique MAC address. 
 
Root Cause
1. Existing loops cause the MAC addresses to drift.
2. The implementation mechanism of the device causes this fault. 
 
Suggestions
The NE80E and NE40E support the learning of MAC addresses only in unqualified mode. When configuring the VPLS, ensure that the MAC address of each VLAN in the same VPLS instance is unique. 

END