SRL L3 EVPN Multi-Homing Lab

This lab showcases L3 EVPN Multi-Homing with centralized routers using SR Linux nodes.

Lab topology

Components

Tested with containerlab version v0.70.2 and SR Linux version 25.7.2.

Deploy lab

All configs are prepared, so you just need to deploy the containerlab file.

clab deploy -t srl-l3-evpn-mh.clab.yml

Network details

The lab consists of 2 spines and 4 leafs forming an EVPN datacenter fabric. The spines act as route reflector but they also participate in the overlay service as centralized routers for the L3 Multi-Homing.

CE1 is connected to Leaf1 and Leaf2 with 2 L3 links (/31). The same applies for CE2 towards Leaf3 and Leaf4.

The leafs are explicitly configured as primary nodes within the ethernet-segment, whereas the centralized routers are implicitly configured as backup - not advertising themselves as next-hop for the ES.

Ethernet-Segment config Leaf

system {
    network-instance {
        protocols {
            evpn {
                ethernet-segments {
                    bgp-instance 1 {
                        ethernet-segment ES-1 {
                            type virtual
                            admin-state enable
                            esi 04:01:01:01:01:00:00:00:00:00
                            multi-homing-mode single-active
                            next-hop 1.1.1.1 {
                                evi 1 {
                                }
                            }
                            df-election {
                                algorithm {
                                    type manual
                                    manual-alg {
                                        primary-evi-range 1 {
                                            end-evi 1
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
            bgp-vpn {
                bgp-instance 1 {
                }
            }
        }
    }
}

Ethernet-Segment config spine (centralized router)

system {
    network-instance {
        protocols {
            evpn {
                ethernet-segments {
                    bgp-instance 1 {
                        ethernet-segment ES-1 {
                            type virtual
                            admin-state enable
                            esi 04:01:01:01:01:00:00:00:00:00
                            multi-homing-mode single-active
                            next-hop 1.1.1.1 {
                                evi 1 {
                                }
                            }
                            df-election {
                                algorithm {
                                    type manual
                                }
                            }
                        }
                        ethernet-segment ES-2 {
                            type virtual
                            admin-state enable
                            esi 04:02:02:02:02:00:00:00:00:00
                            multi-homing-mode single-active
                            next-hop 2.2.2.2 {
                                evi 1 {
                                }
                            }
                            df-election {
                                algorithm {
                                    type manual
                                }
                            }
                        }
                    }
                }
            }
            bgp-vpn {
                bgp-instance 1 {
                }
            }
        }
    }
}