Smarts AM: VLAN information is missing in Smarts AM for a switch connected to a router with sub-interface

Products

• VMware

Issue/Introduction

Symptoms:




VLAN information is missing in Smarts AM for a switch connected to a router with sub-interface

VLAN information is missing in Smarts AM for router configured with the following sub-interface:

Interface GigabitEthernet0/1.11
description RouterName VLAN 11
encapsulation dot1Q 11
ip vrf forwarding INTERNET
ip address x.x.x.x 255.255.255.248
standby 11 ip z.z.z.z
standby 11 priority 120
!

Environment

VMware Smart Assurance - SMARTS

Cause

This problem has been seen when a sub-interface is configured GigabitEthernet0/1.11 but the VLAN is not configured on any neighboring switching systems (all the neighboring systems are Routers), and there is no cable created with this interface. Therefore, the VLAN is associated with the sub-interface GigabitEthernet0/1.11, but this was only for the encapsulation and  does not mean that the VLAN is available in the required router.

The VLAN probe collects VLAN information for the bridges and switches, including VLAN identifiers, trunk ports, and VLAN port memberships. Based on the encapsulation dot1Q 11 configuration line, VLAN 11 is expected to be linked to the interface in Smarts, and the switch is configured as a trunk. Therefore, strictly speaking the VLAN terminates/originates on the PE sub-interface through the encapsulation command. If the VlAN is the mode access on the switch, the encapsulation command should not be required on the PE route. The VLAN information is missing in Smarts because VLANs are port-based or MAC-based and are created in Switches, not for Routers. Quite often there is an Encapsulation to route the VLAN to the router through an Ethernet interface. VLANs are not composed of the Required interface in Routers. A router cannot be composed of VLANs without connection to a switch .

Resolution

To resolve this issue, ensure that a router composed of VLANs is connected to a switch.