Example: Configuring an EVPN-VXLAN Edge-Routed Bridging Fabric with an Anycast Gateway

This example uses the following hardware and software components:

• Two devices that function as transit spine devices.

• Four devices running Junos OS Release 15.1X53-D60 or later software that serve as leaf devices and provide both L2 and L3 gateway functionality.

  • Updated and re-validated using QFX10002 switches running Junos OS Release 21.3R1
• See the hardware summary for a list of supported platforms.

The ERB overlay shown in Figure 2 includes two transit spine devices and four leaf devices that function as both L2 and L3 gateways. Four servers are attached to the leaf devices. Server A is connected to Leaf1 and Leaf2 through a link aggregation group (LAG) interface. On both leaf devices, the interface is assigned the same Ethernet segment identifier (ESI) and set to multihoming all-active mode.

Figure 2: ERB Overlay within a Data Center

In this topology, Server A and Server C are in VLAN 101, Server B is in VLAN 102, and Server D is in VLAN 103. For communication between VLANs to occur, you must configure IRB interfaces for each VLAN on all leaf devices.

The most significant difference between the configuration of ERB compared with CRB is the configuration and location of the L3 gateway. Therefore, this example focuses on the EVPN-VXLAN configuration, in particular, the L3 gateway configuration, on the leaf devices.

For an ERB overlay, you can configure the IRB interfaces within an EVPN instance (EVI) using one of the following methods:

• Method 1—This method entails a unique IP address for each IRB interface, but uses the same MAC for each IRB interface. With this method a single MAC entry is installed for each IRB address on both the leaf devices and servers. For each IRB interface on a particular leaf device, for example, Leaf1, you specify the following:

  • A unique IP address for each IRB interface.

  • The same MAC address is used for each IRB interface.

  For example:

  Table 1: Unique IP Address with Same MAC per IRB Interface

  irb.101	IP address: 10.1.101.254/24	MAC address: 00:00:5e:00:53:01
  irb.102	IP address: 10.1.102.254/24	MAC address: 00:00:5e:00:53:01
  irb.103	IP address: 10.1.103.254/24	MAC address: 00:00:5e:00:53:01

• Method 2—This method entails a unique IP address and MAC for each IRB interface. With this method, a MAC entry is installed for each IRB address on the leaf devices but only a single MAC on the servers. For each IRB interface on Leaf1, you specify the following:

  • A unique IP address for each IRB interface.

  • A unique MAC address is used for each IRB interface..

  For example:

  Table 2: Unique IP Address and MAC per IRB Interface

  irb.101	IP address: 10.1.101.254/24	MAC address: 00:00:5e:00:53:01
  irb.102	IP address: 10.1.102.254/24	MAC address: 00:00:5e:00:53:02
  irb.103	IP address: 10.1.103.254/24	MAC address: 00:00:5e:00:53:03

• Method 3—This method entails a unique IP address and VGA for each IRB interface. With this method a MAC entry is installed for each IRB address and the VGA on the leaf devices and servers. For each IRB interface on Leaf1, you specify the following:

  • A unique IP address for each IRB interface.

  • A unique VGA address for each IRB interface.

  For example:

  Table 3: Unique IP Address and Virtual Gateway Address per IRB Interface

  irb.101	IP address: 10.1.101.1/24	VGA address: 10.1.101.254
  irb.102	IP address: 10.1.102.1/24	VGA address: 10.1.102.254
  irb.103	IP address: 10.1.103.1/24	VGA address: 10.1.103.254

For methods 1 and 2, the same IRB interface configuration is applied across all leaf devices. For method 3, a unique IRB interface address and the same VGA is applied across all leaf devices. In this example, method 1 is used to configure the IRB interfaces.

This example (with method 1) configures the same MAC address for each IRB interface on each leaf device. Each host uses the same MAC address when sending inter-VLAN traffic regardless of where the host is located or which leaf device receives the traffic. For example, in the topology shown in Figure 2, multi-homed Server A in VLAN 101 sends a packet to Server B in VLAN 102. If Leaf1 is down, Leaf2 continues to forward the inter-VLAN traffic even without the configuration of a redundant default gateway MAC address.

When it comes to handling the replication of broadcast, unknown unicast, and multicast (BUM) traffic, note that the configuration on Leaf1:

• includes the set protocols evpn multicast-mode ingress-replication command. This command causes Leaf1, which is a hardware VTEP, to handle replicating and sending BUM traffic instead of relying on a multicast-enabled underlay.

• CLI Quick Configuration
• Configuring EVPN-VXLAN on Leaf1

The section describes the following verifications for this example:

• Verifying BGP
• Verifying the ESI
• Verifying the EVPN Database
• Verifying Connectivity