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Basic MPLS VPN VRF GNS3 Lab

Virtual Routing and Forwarding Table (VRF) allows to create multiple routing tables within a single router. Each of them is assigned to a customer; therefore customers can use the same IP (even private IP) with other customers without confusing the PE router.

GNS3_MPLS_VPN_VRF_topology.jpg

In the above example, R0 is the Provider Edge (PE) router which is on the ISP side while R1 and R2 are customer routers (CustomerA and CustomerB respectively).

R0(config)#ip vrf CustomerA
R0(config-vrf)#rd 1:1
R0(config-vrf)#ip vrf CustomerB
R0(config-vrf)#rd 2:2

The first command “ip vrf CustomerA” enters VRF configuration mode and defines the VPN routing instance by assigning a VRF name (CustomerA).
The second command “rd 1:1” creates routing and forwarding tables. The “rd” command is in the format ASN:nn or IP-address:nn

R0(config)#interface f0/0
R0(config-if)#ip vrf forwarding CustomerA
R0(config-if)#ip address 10.0.0.1 255.255.255.252
R0(config-if)#no shutdown

R0(config)#interface f0/1
R0(config-if)#ip vrf forwarding CustomerB
R0(config-if)#ip address 10.0.0.1 255.255.255.252
R0(config-if)#no shutdown

The “ip vrf forwarding CustomerA” associates the routing and forwarding table “CustomerA” with interface f0/0.

At customer sites we don’t need to do any special configuration, just assign an IP address of each interface and “no shut” them.

R1(config)#interface f0/0
R1(config-if)#ip address 10.0.0.2 255.255.255.252
R1(config-if)#no shutdown

R2(config)#interface f0/0
R2(config-if)#ip address 10.0.0.2 255.255.255.252
R2(config-if)#no shutdown

R0 router recognizes each customer IP by the “Customer name” (CustomerA or CustomerB)

GNS3_MPLS_VPN_VRF_R0_ping_vrf.jpg

Notice that the pings are still successful when two customers use the same IP address.

R1 and R2 can ping to PE router with the same IP

GNS3_MPLS_VPN_VRF_R1_ping.jpg

GNS3_MPLS_VPN_VRF_R2_ping.jpg

We can also see what is inside R0’s VRF table with the “show ip vrf” command

GNS3_MPLS_VPN_VRF_R0_show_ip_vrf.jpg

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