Overview of Flexible Cross-Connect Support on VPWS with EVPN

Access-side Single-homing Support for a VLAN Unaware FXC Service

We support single-homed end devices on access-side router attachment circuits. In this case, all attachment circuits in the same EVI are multiplexed (bundled) into a single EVPN-VPWS service tunnel. This bundle shares a service instance ID and MPLS service label. The access routers advertise only one Ethernet A-D per EVI route for the attachment circuit bundle.

To terminate an attachment circuit bundle at the access router, on the PE device you must configure a separate pseudowire subscriber transport logical interface with the corresponding service instance ID. Do this for each bundle of access interfaces at the access router . The pseudowire subscriber transport logical interface works in VLAN bundle mode.

Access-side Multihoming Support for VLAN Unaware FXC Service

Attachment circuits that share an Ethernet segment identifier (ESI) are bundled together. Attachment circuits in the same group share the same local service instance ID. With FXC multihoming, the access router advertises a separate Ethernet A-D route for each multihomed Ethernet segment. The same PE device acts as the designated forwarder (DF) or non-designated forwarder (NDF) for the attachment circuits in the same Ethernet segment at the same time. However, note that the same PE might also be the DF and NDF independently for different Ethernet segments.

You must use different pseudowire subscriber transport logical interfaces to terminate different multihomed attachment circuit bundles. You can't bundle different multihomed Ethernet segments at the access routers into the same group. This is because the device only has one Ethernet A-D per EVI route for each multihomed Ethernet segment, and each multihomed Ethernet segment must work independently in the forwarding path.

To support interoperability with VLAN unaware multihoming FXC at the access router:

• Bundle attachment circuits on the same multihomed Ethernet segment to use the same local service instance ID on the access router.

• Assign a unique local service instance ID to each attachment circuit bundle.

• At the PE device, use a separate pseudowire subscriber transport logical interface to terminate an access router group of attachment circuits on the same multihomed Ethernet segment.

• Assign a unique local service instance ID corresponding to each pseudowire subscriber transport logical interface.

Here's an example configuration to create a group that bundles the attachment circuits that share the same multihomed ESI. You create the group at the [edit <routing-instances name> protocols evpn] hierarchy level for a VLAN unaware FXC service at an access router as follows:

set routing-instances EVPN-VPWS-FXC-AE protocols evpn group G1 esi 00:71:81:00:00:00:00:00:00:01;
set routing-instances EVPN-VPWS-FXC-AE protocols evpn group G1 interface ge-0/0/3.1;
set routing-instances EVPN-VPWS-FXC-AE protocols evpn group G1 interface ge-0/0/3.2;
set routing-instances EVPN-VPWS-FXC-AE protocols evpn group G1 service-id local 300;
set routing-instances EVPN-VPWS-FXC-AE protocols evpn group G1 service-id remote 300;

Load-Balancing FXC VLAN Aware Service Traffic on PE Devices

To load-balance FXC VLAN aware service traffic on PE devices, you must configure the single-active multihomed Ethernet Segment ID (ESI) under the PS interface with PWHT as shown in the following sample configuration:

Ps0 {
    anchor-point {
        lt-0/2/10;
    }
    flexible-vlan-tagging;
    unit 0 {
        encapsulation ethernet-ccc;
    }
    unit 1 {
        esi {
            00:02:03::01; 
            single-active;
        }
        encapsulation vlan-vpls;
        vlan-id 200;
        family vpls;
    }
    unit 2 {
        esi {
            00:03:03::02; 
            single-active;
        }
        encapsulation vlan-vpls;
        vlan-id 201;
        family vpls;
    }
}

Access Side Single-active with Service Side Single-active

Figure 1 shows a typical square topology with:

• Two service edge routers, PE1 and PE2.

• Two access side PE routers, A-PE1 and A-PE2.

  Note:

  We call the access routers A-PE devices in all of the figures in this document to distinguish them from the service edge routers.

A-PE1 and A-PE2 work in single-active mode. One of the service edge routers is elected as DF. One of the access routers is elected as DF. The DF access router and the DF service edge router have only one active or primary pseudowire between them. If one of the DF PE devices has an access link down or suffers node failure, the NDF PE router becomes the DF. As a result, if the existing primary pseudowire goes down, a new primary pseudowire is established among the DF PE devices. This happens per pseudowire subscriber service logical interface (not per PE device).

Access Side All-active with Service Side Single-active

Figure 2 shows a square topology with:

• Two service edger routers, PE1 and PE2.

• Two A-PE routers, A-PE1 and A-PE2.

A-PE1 and A-PE2 are multihoming peer PE devices in all-active mode for CE devices CE-1 and CE2 on their right side. Both PE devices A-PE1 and A-PE2 can forward the traffic for EVPN-VPWS in this mode.

PE1 and P2 are multihoming peer PE devices in single-active mode for the service. Only one of the PE devices PE1 and PE2 can forward traffic for EVPN-VPWS in this mode. In this figure, PE1 is the DF, so only PE1 forwards the traffic. As a result, this setup establishes two primary pseudowires, one from PE1 to A-PE1 and one from PE1 to A-PE2. To reach CE1 or CE2, PE1 sends the traffic by way of either A-PE1 or A-PE2. PE1 balances the traffic load between those two A-PE devices.