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EVPN Type 2 Symmetric Routing with DCI Stitching

This document outlines the steps necessary to configure symmetric integrated routing and bridging (IRB) of Ethernet VPN (EVPN) Type 2 routes. Layer 2 Data Center Interconnect (DCI) gateway devices perform routing over stitched Virtual Extensible LAN (VXLAN) tunnels. Layer 2 DCI stitching is covered thoroughly in Configure VXLAN Stitching for Layer 2 Data Center Interconnect.

DCI enables you to segment the data center fabric into multiple points of delivery (PODs). Seamless stitching of VXLAN virtual network identifiers (VNIs) allows you to selectively stretch your Layer 2 network between PODs. Each POD follows a spine and leaf design. The leaf nodes in a given POD establish VXLAN tunnels only with leaves and spines in their POD. Spines transport traffic to other spines of different PODs. VXLAN stitching with DCI is ideal for larger networks because it reduces MAC flooding by reducing the required number of VXLAN tunnels between PODs.

Symmetric IRB in an EVPN-VXLAN environment occurs when the ingress and egress VXLAN tunnel end points (VTEPs) perform both routing and bridging on each side of the VXLAN tunnel. The ingress provider edge (PE) device performs a MAC lookup followed by an IP lookup. The egress PE performs the opposite, an IP lookup followed by a MAC lookup. Symmetric versus asymmetric models are covered in RFC 9135.

Note:

Juniper Networks supports symmetric Type 2 routing with EVPN in:

  • Networks using only symmetric Type 2 routing in PODs within the same DCI.

  • EVPN-VXLAN environments.

  • Edge-routed bridging (ERB) overlays.

Figure 1 shows the topology for this example. The topology consists of two data centers connected over a WAN. Both data centers have similar ERB architectures. We refer to the data center on the left as DC1, and the data center on the right as DC2.

DC2 includes a layer of lean spine devices between the gateways and leaf layers. These lean spines are transit devices for the underlay. The topology uses EBGP for both the underlay and the overlay in both DC1 and DC2.

Figure 1: Topology for DCI and Symmetric IRB Routing with EVPN Type 2 Routes Topology for DCI and Symmetric IRB Routing with EVPN Type 2 Routes

Inter-DC Underlay and Overlay

Configure the EBGP DCI underlay on DC2-GW21:

Verify the EBGP DCI underlay on DC2-GW21:

Configure the EBGP DCI overlay on DC2-GW21:

Verify the EBGP DCI overlay on DC2-GW21:

Intra-DC Underlay and Overlay

Configure the EBGP Intra-DC underlay on DC2-GW21:

Verify the EBGP Intra-DC underlay on DC2-GW21:

Layer 2 Symmetric IRB

Configure Layer 2 symmetric IRB interfaces on the DCI gateways Layer 3 virtual routing and forwarding (VRF) instance on DC2-GW21:

Verify symmetric routes on DC2-GW21 for the remote gateway. Symmetric routes will have a protocol preference of 7, while asymmetric routes will have a protocol preference of 170:

Layer 2 symmetric routes carry the Layer 2 and Layer 3 VNIs along with the Type 2 DCI route target (RT) and Type 5 stitching interconnect RT. They also carry router MAC addresses and interconnect Ethernet segment identifiers (iESI) details:

Layer 2 Data Center Interconnect

Configure the VLANs for symmetric routing and seamless stitching. Seamless stitching requires that interconnected gateway devices use the same translation-vni.

Note:

You are required to configure set forwarding-options evpn-vxlan vxlan-trans-vni-enable on QFX5120 series switches to enable Layer 2 stitching. The packet forwarding engine (PFE) will restart once this configuration is applied, resulting in a restart of the associated FPC and interfaces.

Note:

You are required to configure set system packet-forwarding-options system-profile vxlan-stitching on ACX Series routers to enable Layer 2 stitching. The PFE will restart once this configuration is applied.

Note:

You can configure the following parameters on ACX Series routers to enable load balancing based on traffic payload.

Configure the translation VNI on DC2-GW21 for all gateway devices.

Verify the EVPN routes on DC2-GW21 advertised to the DCI. Show the EVPN database for the specified MAC-VRF and VNI. The dci-adv option is specific to showing MAC advertisements to DCI gateway nodes:

Verify the EVPN routes on DC2-GW21 advertised to the data center. Show the EVPN database for the specified MAC-VRF and VNI. The dc-adv statement is specific to showing MAC advertisements to data center gateway nodes:

Configure the interconnect vrf-target and route-distinguisher for DC1 interconnect gateway (iGW) devices on DC1-GW12. These must be different from the vrf-target and route-distinguisher configured for the local DC:

Add the previously defined translation VNIs to the DC1 interconnect configuration under the MAC-VRF:

Configure the interconnect vrf-target and route-distinguisher for DC2 iGW devices. These must be different from the vrf-target and route-distinguisher configured for the local DC:

Add the previously defined translation VNIs to the DC2 interconnect configuration under the MAC-VRF:

Verify the remote VTEP on DC1-GW12:

Verify Type 2 stitching on DC1-GW12:

Verify the remote VTEP on DC2-GW21:

Verify Type 2 Stitching on DC2-GW21:

Configure Layer 2 stitching with non-translated global VNIs on DC2-GW21:

Verify non-translated global VNIs on DC2-GW21:

Verify the EVPN routes advertised to the data center on DC2-GW21:

Type 5 Stitching

Type 5 stitching is Juniper Networks recommended method for advertising the router MAC address. The router MAC address and Layer 3 VNI are how data is forwarded in a stitched environment. Type 2 symmetric routing only carries the Layer 2 and Layer 3 VNI information to the remote gateways and does not perform data forwarding. Configure Type 5 stitching on DC2-GW21:

Verify the Type 5 routes on DC2-GW21 being exported or stitched to the remote gateways and local leaf nodes:

Verify the Type 5 routes on DC2-GW21 being imported or stitched from the remote gateways and the local leaf nodes:

Interconnect Multihoming for DCI Gateway Peers

Configure multihoming on DC2-GW21 for redundancy. A full discussion of multihoming is beyond the scope of this document. For more about multihoming, see EVPN Multihoming Overview.
Note:

You must configure interconnect-multihoming-peer-gateways globally.

It cannot be configured within a MAC-VRF, as shown.

Verify multihoming on DC2-GW21 is working properly. You can see the multihomed peer has the designation of I-ESI-Peer:

Configurations for DC2-GW21 and DC2-Leaf21

Configurations are provided for reference only. Do not copy and paste these configurations as-is into your devices. Configurations for other gateway and leaf nodes will be similar. These configurations have been truncated for readability.

DC2-GW21

Note:

On QFX5130 and QFX5700 switches, also configure the host-profile unified forwarding profile option to support an EVPN-VXLAN environment (see Layer 2 Forwarding Tables for details):

DC2-Leaf21