INTEGRATOR · TWO FABRICS

Dell and Cisco fabrics joined by IOS XR EVPN

Two data centers, two different fabrics: Location A runs Dell SONiC and Location B an ACI-style fabric. Each has two physical domains: a classic switch in VLAN 100, and one in VLAN 200. The fabrics share no control plane. Instead, each hands its VLANs on a tagged, all-active LACP bundle to a pair of IOS XR routers, and those join the sites with EVPN over an MPLS core. Both fabrics’ underlays and the IOS XR core are up. You attach the physical domains, build the hand-offs, and build EVPN.

Integrator track · Dell SONiC-style, Cisco ACI-style, Cisco IOS XR, Cisco switches · 7 objectives

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Objectives

The simulator ticks each one as soon as the network meets it.

At Location A, attach PHY-A1 (VLAN 100) and PHY-A2 (VLAN 200) to L1+L2: PortChannel 10 on port 3 and PortChannel 20 on port 4, with mclag 1.
At Location A, build the hand-off on B1+B2: PortChannel 30 trunking VLANs 100 and 200, with mclag 2, on ports 3 and 4 (one link to each IOS XR router).
At Location B, on the APIC: vPCs VPC-B1 and VPC-B2 to the classic switches and VPC-XR to the IOS XR routers. Then tenant DCI, with bridge domains BD100 and BD200 (flood on) and EPGs E100 and E200 on those vPCs.
On XA1, XA2, XB1 and XB2: Bundle-Ether1 on ports 2 and 3, .100 and .200 l2transport sub-interfaces, the site’s ESI, EVI 100 and 200 with route-targets 65000:100 and 65000:200, and bridge domains V100 and V200.
VLAN 100 crosses: A1-PC reaches B1-PC (192.168.100.22). The far IOS XR router learns its MAC in EVPN.
VLAN 200 crosses too: A2-PC reaches B2-PC (192.168.200.22). The two stay apart: A1-PC cannot reach B2-PC.
The design survives one failure: with XA1 down, A1-PC still reaches B1-PC.

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Before you start

Read it as three domains joined by tagged VLANs: VXLAN inside each fabric, MPLS between the sites, and a plain 802.1Q trunk at each hand-off. That is how different vendors really meet, because neither fabric’s control plane has to understand the other. Each hand-off is one LACP bundle: an MCLAG or vPC pair on one side, and an EVPN all-active segment on the other. Real interworking must be tested on your releases, and a real design also sizes MTU for both encapsulations.

Concept

Joining two fabrics at Layer 2

Two fabrics from different vendors need not share a control plane. Each hands its VLANs over a plain 802.1Q trunk to routers that carry them between sites, here with EVPN over MPLS. Inside each fabric, frames ride VXLAN. On the core, they ride MPLS. At each hand-off they are ordinary tagged frames, which both sides understand.

Concept

Physical domains: joining classic switches to a fabric

Most fabrics must reach racks that know nothing about VXLAN: classic switches and bare-metal servers on tagged VLANs. The fabric treats that network as a physical domain. A leaf pair presents one LACP partner, carries the tagged VLANs on a trunk, and maps each VLAN to a VNI, so a host on a classic switch reaches a host anywhere in the fabric. Only VLANs that are mapped cross, and each stays separate.

Concept

EVPN all-active: one bundle to two PEs

EVPN joins sites at Layer 2 with BGP routes instead of pseudowires. A CE can bundle links to two PEs, because the PEs share an Ethernet Segment Identifier (ESI): LACP sees one partner, and all links carry traffic. Route type 4 lets the PEs of a segment find each other and elect a designated forwarder (DF) per VLAN, which alone sends flooded frames to the CE. Split horizon stops a frame going back to the segment it came from.