IOS XR · EVPN

IOS XR: EVPN all-active with an anycast gateway

Six NCS 5508 PEs, each with two route processors, carry VLANs 10 and 20 across an MPLS core between three sites. The core (IS-IS and LDP), the BGP sessions and Sites 2 and 3 are already configured, so you build Site 1 end to end. Each site has two PEs and two Cisco CE switches. Each CE has one LACP bundle to both of its PEs: the shared ESI makes the two PEs look like one partner. Every PE has the same gateway IP and MAC on a BVI, so hosts always use a gateway at their own site, and the gateway MACs must stay local.

IOS XR track · Cisco IOS XR + Cisco switches · 7 objectives

Open in simulator More IOS XR labs

Objectives

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

On S1-CE1 and S1-CE2, build Port-channel 1 with LACP: four members, trunking VLANs 10 and 20, and the host port in its VLAN.
On S1-PE1 and S1-PE2, build Bundle-Ether 1 (to CE1) and Bundle-Ether 2 (to CE2), each with one member on line card 0/0 and one on 0/1 (bundle id, mode active). Add .10 and .20 l2transport sub-interfaces.
Under evpn, give each bundle its ESI: 00.11.00.00.00.00.00.01.01 for CE1 and 00.11.00.00.00.00.00.01.02 for CE2, the same on both PEs.
Create EVIs 10 and 20 (bgp, rd, route-target 65000:, advertise-mac) and bridge domains V10 and V20 under bridge group SITES, joining the sub-interfaces, the EVI and the gateway.
Build BVI10 and BVI20: 192.168.10.1/24 and 192.168.20.1/24, with MACs 0000.5e00.0110 and 0000.5e00.0120, the same on every PE.
Filter the gateway MACs, so no PE learns them from another PE (mac static-address drop in each bridge domain).
Ping from S1-PC1 to its gateway, to S2-PC1 at another site, and to S1-PC2 in the other subnet.

Start this lab

Before you start

The ESI is what makes all-active work: without the same ESI on both PEs, the CE keeps only the links to one of them. A DF election picks one PE per VLAN to send flooded traffic to the CE. Split horizon stops a frame going back to the segment it came from. show evpn evi mac shows a gateway MAC learned from another PE as a move. Two line cards mean a bundle survives losing one. On real routers, the exact command for this MAC filter varies by release, so check yours.

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.

Concept

Anycast gateway: one gateway on every PE

Each PE has a routed interface on the bridge domain (a BVI on IOS XR, a Vbdif on Huawei), and all of them use the same IP and MAC. A host always reaches a gateway at its own site, and keeps the same gateway if it moves. But the same MAC on every PE must not travel as an EVPN route: a PE would then see its own gateway MAC behind another PE, as if it had moved.