Understanding How to Configure VXLANs on QFX5110 Switches and Layer 3 Logical Interfaces to Interoperate

 

In the EVPN-VXLAN network segments shown in Figure 1 (Before), hosts A and B need to exchange traffic. When host A sends a packet to host B or vice versa, the packet must traverse the following networking entities:

  • On QFX5110 switch: a pure Layer 3 logical interface configured using the set interfaces interface-name unit logical-unit-number family inet address ip-address/prefix-length or the set interfaces interface-name unit logical-unit-number family inet6 address ipv6-address/prefix-length command.

  • A VXLAN tunnel between the QFX5110 switch and the QFX10002 switch.

  • On QFX10002 switch: a pure Layer 3 logical interface configured as described in the first bullet.

Figure 1: Results When Routing Traffic Between a VXLAN and a Layer 3 Logical Interface Is Disabled (Before) and Enabled (After)
Results When Routing
Traffic Between a VXLAN and a Layer 3 Logical Interface Is Disabled
(Before) and Enabled (After)

By default, routing traffic between a VXLAN and a Layer 3 logical interface is disabled. When this functionality is disabled, the pure Layer 3 logical interface on the QFX5110 switch drops Layer 3 traffic from host A and VXLAN-encapsulated traffic from the QFX10002 switch. To prevent the pure Layer 3 logical interface on the QFX5110 switch from dropping this traffic, you can perform some additional configuration on the QFX5110 switch.

The additional configuration on the QFX5110 switch entails the following on a physical interface (Figure 1 (After)):

  • Reconfiguring the pure Layer 3 logical interface as a Layer 2 logical interface and associating this interface with a dummy VLAN and a dummy VXLAN network identifier (VNI).

  • Creating an IRB interface, which provides Layer 3 functionality within the dummy VLAN.

For example:

In lieu of the original pure Layer 3 logical interface, the newly created Layer 2-Layer 3 logical interfaces can now handle Layer 3 traffic from host A and VXLAN-encapsulated traffic from the QFX10002 switch.