3
Terminology
Edge device
An edge device performs typical Layer 2 learning and forwarding on the site-facing interfaces
(internal interfaces) and performs tunneling and routing on the transport-facing interfaces.
EVI network ID
An edge device can belong to multiple EVI networks. Each EVI network is uniquely identified by a
network ID.
EVI link
An EVI link is a bidirectional virtual Ethernet channel between a pair of edge devices in an EVI
network. EVI links are conveyed on EVI tunnels. Each EVI link is uniquely identified by a pair of
source and destination EVI tunnel IP addresses.
EVI tunnel
An EVI tunnel is a point-to-many automatic GRE tunnel that conveys EVI links for an EVI network.
One EVI tunnel can provide services only for one EVI network.
EVI neighbor
All edge devices in an EVI network are EVI neighbors to one other.
ENDP
EVI Neighbor Discovery Protocol uses the client/server model to dynamically discover sites and
edge devices, establish and maintain EVI links, and exchange network membership information in
an EVI network.
ENDS
An EVI neighbor discovery server maintains all neighbor information in an EVI network. An EVI
network can have up to two ENDSs.
ENDC
An EVI neighbor discovery client works with an ENDS to learn neighbor information and triggers EVI
link setup between neighbors.
EVI IS-IS
EVI IS-IS establishes adjacencies and advertises MAC reachability information among edge devices
at different sites in an EVI network.
EVI IS-IS runs independently of the Layer 3 routing protocols on the transport network and sites.
DED
A DED is elected from between the edge devices on each EVI link to send CSNP packets for LSDB
synchronization.
Internal interface
Internal interfaces are site-facing Layer 2 interfaces that connect an edge device to switches or
routers in the site.
Working mechanism
An edge device uses the following process to set up an EVI network and forward traffic at Layer 2 to
remote sites:
1.
Runs ENDP to discover EVI neighbors and set up EVI links between neighbors.
2.
Runs EVI IS-IS to advertise MAC reachability information over EVI links in the EVI network.
