3
Working mechanisms
The VTEP uses the following process to forward an inter-site frame:
1. Assigns the frame to its matching VXLAN if the frame is sent between sites.
2. Performs MAC learning on the VXLAN's VSI.
3. Forwards the frame through VXLAN tunnels.
This section describes this process in detail. For intra-site frames in a VSI, the system performs
typical Layer 2 forwarding, and it processes 802.1Q VLAN tags as described in "Access mode of
VSIs."
Assignment of traffic to VXLANs
Traffic from the local site to a remote site
The VTEP uses an Ethernet service instance to match customer traffic on a site-facing interface. The
VTEP assigns customer traffic to a VXLAN by mapping the Ethernet service instance to a VSI.
An Ethernet service instance is identical to an attachment circuit (AC) in L2VPN. An Ethernet service
instance matches a list of VLANs on a Layer 2 Ethernet interface by using a frame match criterion.
The frame match criterion specifies the characteristics of traffic from the VLANs, such as tagging
status and VLAN IDs.
As shown in Figure 3, Ethernet
service instance 1 matches VLAN 2 and is mapped to VSI A (VXLAN
10). When a frame from VLAN 2 arrives, the VTEP assigns the frame to VXLAN 10, and looks up VSI
A's MAC address table for the outgoing interface.
Figure 3 Identifying traffic from the local site
Traffic from a remote site to the local site
When a frame arrives at a VXLAN tunnel, the VTEP uses the VXLAN ID in the frame to identify its
VXLAN.
MAC learning
The VTEP performs source MAC learning on the VSI as a Layer 2 switch.
• For traffic from the local site to the remote site, the VTEP learns the source MAC address before
VXLAN encapsulation.
• For traffic from the remote site to the local site, the VTEP learns the source MAC address after
removing the VXLAN header.
A VSI's MAC address table includes the following types of MAC address entries:
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