H3C Technologies H3C S12500 Series Switches - Manual (Page 9)

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• Site and transport transparency—EVI is both site and transport network transparent. It has no
special site or transport network topology requirements.
• Easy management and maintenance—EVI requires deployment only on edge devices and does not
introduce any topology change or configuration within sites or the transport network.
Network topologies
As shown in Figure 2 , an EVI network comprises one or multiple edge devices at each site. These sites are
connected through virtual links across an IP-based transport network and run the EVI IS-IS protocol to
advertise their MAC address entries to each other. EVI maintains MAC routing information on the edge
devices without changing the forwarding or routing information within the sites or the transport network.
Figure 2 EVI network
EVI supports multiple EVI networks on an edge device for extending different VLANs across the Layer 3
network. One EVI network can convey multiple VLANs, but one VLAN can map to only one EVI network.
Each EVI network has separate network parameters and independently forwards traffic.
As shown in
Figure 3 , EVI network 1 extends VLAN 100 and VLAN 101 to Site 2, Site 3, and Site 4 for
Web access traffic. EVI network 2 extends VLAN 4000 (the management VLAN) to all sites, and EVI
network 3 extends VLANs 50 to 80 between Site 1 and Site 4 for database traffic.
Transport network
Site network
Edge
device
EVI link
EVI
Site network
Edge device
Site
network
Edge device
EVI link EVI link
VLAN 10
VLAN 10
VLAN 10
Site 1
Site 2
Site 3