Ethernet Segment Routes are needed in multi-homing scenario and used for Designated Forwarder Election. Designated Forwarder is responsible for sending broadcast, unknown multicast and multicast (BUM) traffic to the CE on a particular Ethernet Segment.
RFC 7432 allows selecting a DF at the granularity of <ES, VLAN> for VLAN-based service and <ES, VLAN bundle> for VLAN-aware service. This enables load-balancing of BUM traffic at a VLAN or VLAN-bundle level.
Continue reading “EVPN Type 4 (Ethernet Segment route) Explained”
Type 3 routes are required for Broadcast, Unknown Unicast and Multicast (BUM) traffic delivery across EVPN networks. Type 3 advertisements provide information about P-tunnels that should be used to send BUM traffic.
Without Type 3 advertisements, ingress router would not know how to deliver BUM traffic to other PE devices that comprise given EVPN instance.
Continue reading “EVPN Type 3 (Inclusive Multicast Ethernet Tag route) Explained”
Type 2 routes are used to advertise MAC addresses and IP addresses that might be associated with aforementioned MAC addresses.
In order to advertise Type 2 routes, PE needs to learn MAC addresses from the directly attached CEs. This is done via normal data-plane learning mechanisms. RFC 7432 also allows for MAC address learning via control plane interaction between PE and CE, although we have not see this implemented by any vendors.
Continue reading “EVPN Type 2 (MAC/IP Advertisement route) Explained”
Type 1 advertisements are used for two distinct functions – Fast Convergence and Aliasing. EVPN Fast Convergence allows PE devices to change the next-hop adjacencies for all MAC addresses associated with a particular Ethernet Segment. EVPN aliasing allows traffic to be balanced across multiple egress points.
Type 1 routes are only advertised if Ethernet Segment Identifier is set to non-zero value, meaning that Type 1 routes are only originate for multi-homed sites.
Please refer to the following cheatsheet if you are not familiar with EVPN Terminology.
Continue reading “EVPN Type 1 (Ethernet Auto-Discovery) Explained”