What is VRF?
Virtual routing and forwarding (VRF) IP technology allows users to configure multiple routing table instances to simultaneously co-exist within the same router. Overlapping IP addresses can be used without conflicting because the multiple routing instances are independent, and can select different outgoing interfaces.
VRFs are used for network isolation/virtualization at Layer 3 of the OSI model as VLANs serve similarly at Layer 2. Typically, users implement VRFs primarily to seperate network traffic and more efficiently use network routers. Virtual routing and forwarding can also create VPN tunnels to be solely dedicated to a single network or client.
Here are the key aspects of VRF in more detail:
1. Routing Table Separation: With VRF, each virtual network or routing domain has its own dedicated routing table. This means that the routing information for one VRF is kept separate from other VRFs. Each VRF maintains its own set of routes, routing protocols, and routing decisions.
2. Interface Segregation: In addition to separate routing tables, VRF also allows for interface segregation. Each VRF can have its own set of interfaces, which are associated exclusively with that VRF. This ensures that the traffic within a particular VRF remains isolated from other VRFs.
3. Traffic Isolation: The primary purpose of VRF is to provide traffic separation and isolation. Each VRF operates as a completely independent routing domain, enabling the network administrator to keep the traffic of different entities, customers, or network segments separated from one another.
4. Independent Forwarding Decisions: VRF allows for independent forwarding decisions within each virtual routing domain. The forwarding decisions are made based on the routing table associated with the specific VRF. This ensures that traffic destined for a particular VRF is correctly routed within its dedicated routing domain.
5. VPN Support: VRF is often used as a foundation for implementing virtual private networks (VPNs). By leveraging VRF, network administrators can create VPNs that provide secure and isolated communication between different sites or customers, using a shared physical infrastructure.
6. Scalability and Flexibility: VRF offers scalability and flexibility in network design. It allows for the efficient utilization of network resources by consolidating multiple routing domains onto a single physical device. This eliminates the need for separate hardware for each routing domain, resulting in cost savings and simplified network management.
7. Management and Configuration: VRFs can be configured and managed through the device's command-line interface (CLI) or graphical user interface (GUI). The network administrator assigns interfaces, configures routing protocols, and defines the routing tables associated with each VRF.
VRF is a powerful feature that provides network segmentation, traffic isolation, and VPN capabilities. It is widely used in various networking scenarios, including multi-tenant environments, enterprise networks, and service provider networks.
What is VRF Lite:
VRF Lite, or Virtual Routing and Forwarding Lite, is a simplified version of the Virtual Routing and Forwarding (VRF). It allows the creation of multiple virtual routing tables within a single physical device, providing Logical network segmentation and isolation.
Although it doesn't have fancy features like MPLS, it still provides the basic function of keeping traffic from different domains separate. It's a simpler version of VRF that's useful for smaller networks or simpler setups where you want to isolate and control traffic without too much complexity. You can take analogy of VLAN.
It is commonly used in smaller-scale deployments or simpler network setups to achieve traffic separation and isolation without the resource overhead and complexity of full-scale VRF implementations.
In summary, VRF provides advanced features and complete isolation at the cost of additional complexity and resource overhead. On the other hand, VRF Lite offers simplified configuration and management, suitable for smaller-scale deployments that don't require advanced features like MPLS.
Comparison Table for VRF and VRF Lite:
How to Configure VRF and VRF-Lite Route Leak:
Below is the diagram where we can see that how we can separate 3 different Department/Business unit using VRF.
Figure: 1.1
In figure 1.1 you can see that how VRF Lite can separate 3 different Business Unit even though they are using common Internet.
Now the same we will test in LAB and learn how to configure. The LAB diagram is in below.
Figure: 1.2
Now below is the configuration of both Router-1 and 2.
Router-1
ip vrf BU-A
description Business-Unit-A
!
ip vrf BU-B
description Business-Unit-B
!
ip vrf BU-C
description Business-Unit-C
!
interface FastEthernet0/0
ip address 8.8.8.1 255.255.255.0
duplex full
!
interface Ethernet1/1
ip vrf forwarding BU-A
ip address 192.168.10.1 255.255.255.0
duplex full
!
interface Ethernet1/2
ip vrf forwarding BU-B
ip address 172.16.10.1 255.255.255.0
duplex full
!
interface Ethernet1/3
ip vrf forwarding BU-C
ip address 10.10.10.1 255.255.255.0
duplex full
!
interface Ethernet1/4
ip vrf forwarding BU-A
ip address 192.168.20.1 255.255.255.0
duplex full
!
interface Ethernet1/5
ip vrf forwarding BU-B
ip address 172.16.20.1 255.255.255.0
duplex full
!
interface Ethernet1/6
ip vrf forwarding BU-C
ip address 10.10.20.1 255.255.255.0
duplex full
!
!
!
ip route 10.10.10.0 255.255.255.0 Ethernet1/3
ip route 10.10.11.0 255.255.255.0 Ethernet1/3
ip route 10.10.30.0 255.255.255.0 Ethernet1/6
ip route 10.10.33.0 255.255.255.0 Ethernet1/6
ip route 172.16.10.0 255.255.255.0 Ethernet1/2
ip route 172.16.11.0 255.255.255.0 Ethernet1/2
ip route 172.16.20.0 255.255.255.0 Ethernet1/5
ip route 172.16.30.0 255.255.255.0 Ethernet1/5
ip route 172.16.33.0 255.255.255.0 Ethernet1/5
ip route 192.168.10.0 255.255.255.0 Ethernet1/1
ip route 192.168.11.0 255.255.255.0 Ethernet1/1
ip route 192.168.20.0 255.255.255.0 Ethernet1/4
ip route 192.168.30.0 255.255.255.0 Ethernet1/4
ip route 192.168.33.0 255.255.255.0 Ethernet1/4
ip route vrf BU-A 8.8.8.0 255.255.255.0 8.8.8.8 global
ip route vrf BU-A 192.168.11.0 255.255.255.0 192.168.10.100 name TO-BU-A-User
ip route vrf BU-A 192.168.30.0 255.255.255.0 192.168.20.2 name To-Tower-2
ip route vrf BU-A 192.168.33.0 255.255.255.0 192.168.20.2 name To-Tower-2-BU-A-User
ip route vrf BU-B 8.8.8.0 255.255.255.0 8.8.8.8 global
ip route vrf BU-B 172.16.11.0 255.255.255.0 172.16.10.100 name TO-Tower-1-BU-B-User
ip route vrf BU-B 172.16.30.0 255.255.255.0 172.16.20.2 name To-Tower-2
ip route vrf BU-B 172.16.33.0 255.255.255.0 172.16.20.2 name To-Tower-2-BU-B-User
ip route vrf BU-C 8.8.8.0 255.255.255.0 8.8.8.8 global
ip route vrf BU-C 10.10.11.0 255.255.255.0 10.10.10.100 name TO-Tower-1-BU-C-User
ip route vrf BU-C 10.10.30.0 255.255.255.0 10.10.20.2 name To-T-2-BU-C
ip route vrf BU-C 10.10.33.0 255.255.255.0 10.10.20.2 name To-Tower-2-BU-C-User
!
!
Router-2
ip vrf BU-A
description Business-Unit-A
!
ip vrf BU-B
description Business-Unit-B
!
ip vrf BU-C
description Business-Unit-C
!
interface Ethernet1/1
ip vrf forwarding BU-A
ip address 192.168.30.1 255.255.255.0
duplex full
!
interface Ethernet1/2
ip vrf forwarding BU-B
ip address 172.16.30.1 255.255.255.0
duplex full
!
interface Ethernet1/3
ip vrf forwarding BU-C
ip address 10.10.30.1 255.255.255.0
duplex full
!
interface Ethernet1/4
ip vrf forwarding BU-A
ip address 192.168.20.2 255.255.255.0
duplex full
!
interface Ethernet1/5
ip vrf forwarding BU-B
ip address 172.16.20.2 255.255.255.0
duplex full
!
interface Ethernet1/6
ip vrf forwarding BU-C
ip address 10.10.20.2 255.255.255.0
duplex full
!
no ip http server
no ip http secure-server
ip route vrf BU-A 8.8.8.0 255.255.255.0 192.168.20.1
ip route vrf BU-A 192.168.10.0 255.255.255.0 192.168.20.1 name To-Tower-1
ip route vrf BU-A 192.168.11.0 255.255.255.0 192.168.20.1 name TO-Tower-1-BU-A-User
ip route vrf BU-A 192.168.33.0 255.255.255.0 192.168.30.100 name To-Tower-2-BU-A-User
ip route vrf BU-B 8.8.8.0 255.255.255.0 172.16.20.1
ip route vrf BU-B 172.16.10.0 255.255.255.0 172.16.20.1 name To-T1-BU-B
ip route vrf BU-B 172.16.11.0 255.255.255.0 172.16.20.1 name To-T1-Users
ip route vrf BU-B 172.16.33.0 255.255.255.0 172.16.30.100
ip route vrf BU-C 8.8.8.0 255.255.255.0 10.10.20.1
ip route vrf BU-C 10.10.10.0 255.255.255.0 10.10.20.1 name To-T1-BU-C
ip route vrf BU-C 10.10.11.0 255.255.255.0 10.10.20.1 name To-T1-BU-C-User
ip route vrf BU-C 10.10.33.0 255.255.255.0 10.10.30.100 name To-BU-C-T2-User
Below picture describe how The route Leak works
Figure 1.3
Now we will check how all the unit can separated and how they can access same internet.
Figure 1.4
Here you can see how each other isolated. and below Figure 1.5 show how they can use same internet.
Figure 1.5
Here is Video Tutorial Link: https://youtu.be/kmtRSVaYxZg
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