H3C S7500E Series Manual page 11

Figure 4 Layer 2 forwarding in a site
MAC table
VLAN MAC Interface
200 MAC1 GE1/0/1
200 MAC2 GE1/0/2
GE1/0/1
Host A
MAC1
Site 1
The following forwarding process (see
1. The source edge device learns the source MAC address of the incoming Ethernet frame, and
looks up the destination MAC address in its MAC table for the outgoing interface.
2. If the outgoing interface is an EVI-Link interface instead of a physical port, the source edge
device encapsulates the frame in a GRE header, and then adds an IP header and a link layer
protocol header.
In the outer IP header, the source IP address is the source edge device's tunnel source IP
address, and the destination IP address is the destination edge device's tunnel source IP
address.
3. The source edge device forwards the encapsulated packet out of the EVI link to the destination
edge device across the IP transport network.
4. The destination edge device removes the headers of the original Ethernet frame, looks up the
destination MAC address in the MAC address table, and sends the frame out of the matching
outgoing interface.
Transport network
EVI
EVI
GE1/0/2
Host B
MAC2
Figure 5) takes place for unicast flows between sites:
5
EVI
Site 2