Figure 70: EVPN Operation
EVPN can operate in single homing or dual homing mode. Consider single homing scenario, when EVPN is
enabled on PE, routes are advertised where each PE discovers all other member PEs for a given EVPN instance.
When an unknown unicast (or BUM) MAC is received on the PE, it is advertised as EVPN type-2 routes to
other PEs. MAC routes are advertised to the other PEs using EVPN type-2 routes. In multi-homing scenarios
Type 1, 3 and 4 are advertised to discover other PEs and their redundancy modes (single active or active-active).
Use of Type-1 route is to auto-discover other PE which hosts the same CE. The other use of this route type
is to fast route unicast traffic away from a broken link between CE and PE. Type-4 route is used for electing
designated forwarder. For instance, consider the topology when customer traffic arrives at the PE, EVPN
MAC advertisement routes distribute reachability information over the core for each customer MAC address
learned on local Ethernet segments. Each EVPN MAC route announces the customer MAC address and the
Ethernet segment associated with the port where the MAC was learned from and is associated MPLS label.
This EVPN MPLS label is used later by remote PEs when sending traffic destined to the advertised MAC
address.
EVPN Route Types
The EVPN network layer reachability information (NLRI) provides different route types.
Table 6: EVPN Route Types
UsageNameRoute Type
Few routes sent per ES, carry the
list of EVIs that belong to ES
Ethernet Auto-Discovery (AD)
Route
1
Advertise MAC, address
reachability, advertise IP/MAC
binding
MAC/IP Advertisement Route2
Multicast Tunnel End point
discovery
Inclusive Multicast Ethernet Tag
Route
3
Redundancy group discovery, DF
election
Ethernet Segment Route4
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
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EVPN Features
EVPN Route Types
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