[NE Router-Troubleshooting] Network Segments Cannot Successfully Ping Each Other In Dot1q Termination Access

Fault Symptom

Users on the network segment A access the router through the BAS; users on the network segment B access the router through the sub-interface for Dot1q VLAN tag termination on the router. After ping operations are performed between network segment A and network segment B, it is found that some addresses cannot successfully ping each other. The router, however, can successfully ping both network segment A and network segment B.

Fault Analysis

1.     Run the display this command in the view of sub-interfaces of GE 1/0/0 on the router to view information about the sub-interfaces of GE 1/0/0. The information is displayed as follows:

#

interface GigabitEthernet1/0/0.1

 control-vid 10 dot1q-termination

 dot1q termination vid 3

 ip address 10.1.1.1 255.255.255.0

 arp broadcast enable

#

interface GigabitEthernet1/0/0.2

 undo shutdown

 vlan-type dot1q 10

 ip address 10.1.1.2 255.255.255.0

#

2.     Run the display this command in the view of sub-interfaces of GE 2/0/0 on the router to view information about the sub-interfaces of GE 2/0/0. The information is displayed as follows:

#

interface GigabitEthernet2/0/0.1

 undo shutdown

 vlan-type dot1q 10

 ip address 10.2.1.1 255.255.255.0

#

interface GigabitEthernet2/0/0.2

 undo shutdown

 vlan-type dot1q 10

 ip address 10.2.1.2 255.255.255.0

#

3.     You can find that GE 1/0/0.1 is configured as the sub-interface for Dot1q VLAN tag termination, whereas other sub-interfaces are configured to terminate VLAN packets through the vlan-type dot1q command. If a user needs to access the router through a sub-interface for Dot1q VLAN tag termination and also supports network segment routes, it is required that rt-protocol be configured and the configured user VLAN ID be the same as the control VLAN ID. In this case, you can change the configuration of GE 1/0/0.1 to rectify the fault.

Procedure

1.     Run the system-view command to enter the system view.

2.     Run the interface interface-type interface-number command to enter the sub-interface view.

3.     Run the control-vid vid dot1q-termination rt-protocol command to configure the control VLAN for the sub-interface for Dot1q VLAN tag termination.

4.     Run the vlan-group group-id command to configure a user VLAN group.

5.     Run the statistic enable command to enable the QinQ statistics function for the user VLAN group on the sub-interface.

6.     Run the quit command to return to the sub-interface view.

7.     Run the dot1q termination vid low-pe-vid vlan-group group-id command to configure the sub-interface for Dot1q VLAN tag termination.

After the preceding operations, network segment A and network segment B can successfully ping each other.

Summary

Network segment A is connected to the router through the BAS. Therefore, the router can successfully ping network segment A. The router is directly connected to network segment B at Layer 2. Therefore, the router can successfully ping network segment B.

Some addresses on network segment A and network segment B cannot successfully ping each other due to incorrect Dot1q termination configurations of a sub-interface on the router. If a user needs to access the router through a sub-interface for Dot1q VLAN tag termination and also supports network segment routes, it is required that rt-protocol be configured and the configured user VLAN ID be the same as the control VLAN ID.