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DES-7200 Configuration Guide Chapter 6 BGP
Configuration
6-41
As shown in Figure 16, two VPN sites on the left side (VPN1 and VPN2) are
connected to the MPLS backbone network through an MCE device. Users of
VPN1 and VPN2 need to establish VPN tunnels with remote users of VPN1 and
VPN2. With MCE enabled, routing tables can be created for VPN1 and VPN2
individually on MCE device; VLAN-interface 2 can be bound to VPN1, and
VLAN-interface 3 can be bound to VPN 2. When receiving a piece of routing
information, MCE determines the source of the routing information according to
the number of the interface receiving the information and then maintains the
corresponding VPN routing table accordingly. Meanwhile, you also need to bind
the MCE-connecting interfaces on PE1 to the VPNs in the same way as those on
the MCE device. The MCE device is connected to PE1 through a trunk, which
permits packets of VLAN2 and VLAN3 with VLAN tags carried. In this way, PE1
can determine the VPN to which a received packet belongs according to the
VLAN tag of the packet and passes the packet to the corresponding tunnel.
How does MCE device accurately transmit the private routing information of
multiple VPN instances to PEs? This involves two steps: routing information
exchange between MCE and VPN site, and routing information exchange
between MCE and PE. There are multiple ways to exchange routing information,
such as static route, RIP, OSPF, ISIS and BGP. If BGP routing protocol is utilized
to exchange routing information, BGP MCE is then used, namely BGP MCE
allows BGP protocol to support VRF and enable BGP routing information
exchange under VRF. We need to configure BGP peer for each VRF instance on
MCE and introduce IGP routing information of corresponding VPN. Since each
VPN is generally in different AS, EBGP is therefore used to advertise routes.
6.25.3 Default configurations
The following table describes the default configurations of BGP MCE.
Function Default setting
VRF instance No VRF instance is created by default.
BGP-VRF binding No BGP-VRF binding by default
6.25.4 Configuring VRF instance and route-related attributes
Before configuring BGP MCE, VRF instance and route-related attributes must be
configured first:
Command Function
DES-7200 # configure terminal
Enter global configuration mode
DES-7200(config)# ip vrf VRF1
Create a VRF named VRF1 and enter VRF
mode.