Users in Vlan 6 need to communicate with users in VLAN 5 over an ISP network. The carrier assigns VLAN 10 as the stack VLAN (S-VLAN). Single -tag VLAN mapping is configured on GE0/0/1 of switchC and SwitchD to map customer VLANs (CVLANs) 5 and 6 to S-VLAN 10. 

Handling Process:

After VLAN mapping is configured on the interfaces, users in different VLANs cannot communicate with each other. Teh fault is commonly caused by one of the following:

1. The translated VLAN is either not communicated with each other has not been created.

2. The interface s configured with VLAN mapping are not added to the translated VLAN.

The translated VLAN ID configured on SwitchC and SwitchD is different from the SVLAN ID assigned by the carrier.

The interfaces configured with the VLAN mapping are faulty.

Root Cause

This is issue only can be happen by human mistake not configuring all the ports, VLANs & switches properly.

For large network it will take time to identify if there is slight mistaken in the network configuring.

The problem can be bypassed following bellow solution to check one-by-one, whether the problem actually lies.

Solution

We have to do one by one checking in each access switch to find the appropriate solution:

Initial Checking: 

Check that the translated VLAN (specified by map-vlan) has been created.
Run the display vlan command on SwitchC and SwitchD to check whether the translated VLAN has been created.

b. If the translated VLAN has not been created, run the vlan command to create it.
a. If the translated VLAN has been created, go to step 2.

Afterwards:

Needs to check that the interfaces configured with VLAN mapping have been added to the translated VLAN in tagged mode.
Run the display this command on the interfaces configured with VLAN mapping to check whether the interfaces have been added to the translated VLAN in tagged mode.

If it's still not been translated:

Needs to check that the translated VLAN ID configured on SwitchC and SwitchD is the same as the SVLAN ID assigned by the carrier.
Run the display this command on the interfaces configured with VLAN mapping to check whether the translated VLAN ID is the same as the S-VLAN ID assigned by the carrier.

Finally:

Needs to check that the user-side interfaces are in the C-VLANs.
Run the display vlan vlan-id command on SwitchA and SwitchB to check whether the user side interfaces are in the C-VLANs.
f the user-side interfaces are not in the C-VLANs, run the port trunk allow-pass vlan,
port hybrid tagged vlan, or port default vlan command to add the interfaces to the CVLANs.

Suggestion and Summary

Please do note that, savings the results of each troubleshooting step is recommended. If troubleshooting fails to correct the fault, you will have a record of your actions to provide Huawei technical support personnel.

Also, please do consider following aspects before doing details further troubleshooting:

1. VLAN mapping can only be configured on trunk or hybrid interface, and the interface must be added to the translated VLAN in tagged mode.

2. If a range of original VLANs is specified by vlan-id1 to vlan-id2 on an interface, the the interface must be added to all the original VLANs in tagged mode, and the translated VLAN cannot have a VLANIF interface.

3. Limiting MAC address learning on an interface may affect N:1 VLAN mapping on the interface.
4. If the interfaces configured with VLAN mapping have not been added to the translated VLAN in tagged mode, run the port trunk allow-pass vlan or port hybrid tagged vlan command in the interface views to add the interfaces to the translated VLAN in tagged mode.
5. If the interfaces have been added to the translated VLAN in tagged mode, go to solution method.