Mpls L3Vpn Networking Schemes - 3Com MSR 50 Series Configuration Manual

1464 C 79: MPLS L3VPN C
HAPTER
MPLS L3VPN
Networking Schemes
ONFIGURATION
If two sites (CEs) belong to the same VPN and are connected to the same PE, each
of them only needs to know how to reach the remote CE.
The following takes
forwarding procedure.
Figure 407 VPN packet forwarding
Site 1 CE 1
PE 1
1.1.1.1/24
1.1.1.2
Site 1 sends an IP packet with the destination address of 1.1.1.2. CE 1 transmits
the packet to PE 1.
1 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.
2 The MPLS backbone transmits the packet to PE 2 by outer label. Note that the
outer label is removed from the packet at the penultimate hop.
3 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 the interface to CE 2.
4 CE 2 transmits the packet to the destination by IP forwarding.
In MPLS L3VPNs, VPN 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 this networking scheme, the basic VPN networking scheme, you need to
assign a VPN target to each VPN for identifying the export target attribute and
import target attribute of the VPN. Moreover, this VPN target cannot be used by
any other VPNs.
Figure 407 as an example to illustrate the VPN packet
P P
Layer1
Layer2
Layer2
1.1.1.2
1.1.1.2
CE 2 Site 2
PE 2
1.1.1.2/24
1.1.1.2