Mpls L3Vpn Networking Schemes - HP HSR6800 Configuration Manual

Figure 67 VPN packet forwarding
Site 1
2.1.1.1/24
1.1.1.2
A VPN packet is forwarded in the following way:
1. Site 1 sends an IP packet with the destination address of 1.1.1.2. CE 1 transmits the packet to
PE 1.
2. PE 1 searches VPN instance entries based on the inbound interface and destination address of
the packet. Once finding a matching entry, PE 1 labels the packet with both inner and outer
labels and forwards the packet out.
3. The MPLS backbone transmits the packet to PE 2 by outer label. The outer label is removed
from the packet at the penultimate hop.
4. PE 2 searches VPN instance entries according to the inner label and destination address of the
packet to determine the outbound interface and then forwards the packet out of the interface to
CE 2.
5. CE 2 transmits the packet to the destination by IP forwarding.

MPLS L3VPN networking schemes

In MPLS L3VPNs, route target attributes are used to control the advertisement and reception of VPN
routes between sites. They work independently and can be configured with multiple values to
support flexible VPN access control and implement multiple types of VPN networking schemes.
Basic VPN networking scheme
In the simplest case, all users in a VPN form a closed user group. They can forward traffic to each
other but cannot communicate with any user outside the VPN.
For the basic VPN networking scheme, you must assign a route target to each VPN for identifying
the export target attribute and import target attribute of the VPN. Moreover, this route target cannot
be used by any other VPNs.
CE 1
P
PE 1
Layer1
Layer2
1.1.1.2
P
PE 2
Layer2
1.1.1.2
1.1.1.2
241
Site 2
CE 2
1.1.1.2/24