Have a look at the routing table. Below, the ping to This happens because the ping is using the default VRF. The ISP networks are reachable. There are two ways to approach this. This provides the best traffic isolation, but there is a limited number of processes.
The other way is to run OSPF as a single process. What if you want to share routes? There are two ways to do this. This is an interesting topic, but is beyond the scope of this article. The other is with traffic hair-pinning. This is going to build on the previous example. In this case, the firewall can have an interface connected to each VRF on the switch.
This might be two physical interfaces, or a single physical interface with sub-interfaces. The switch and firewall both run OSPF. Traffic from tenant-1 passes to the switch, then out of the VRF to the firewall. The static routes are also removed. The difference is that the next hop for other tenant networks is the firewall, which OSPF learns. Ping and traceroute show that traffic between tenants is passing through the firewall.
This allows the firewall to inspect the traffic, and apply security policies. You must be logged in to post a comment. A VRF is a virtual routing table. This lab will only use the IPv4 address family. Buy or Renew. Find A Community. Cisco Community. Join us in congratulating October's Spotlight Award Winners! Turn on suggestions. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for. Search instead for. Did you mean:. All Community This category This board. Hi everyone, We have a network with three routers, where we differentiate client services via VRFs. Thanks in advance. Best regards, Marta Solved! Labels: Labels: Other Service Providers. I have this problem too. All forum topics Previous Topic Next Topic. For starters, the easiest approach would be to throw additional dedicated hardware at the problem — we could install additional store-and-match-thingies e.
TCAM as well as forwarding-thingies e. ASICs into the box to process the traffic for the newly created routing instances. But the drawbacks of this approach are immediately obvious:. Store-and-match-thingies tend to be both expensive and power-hungry — the price of our devices and the price of running them with hardware VRFs would skyrocket; Same thing applies for the forwarding-engine thingies, maybe even more so; Scalability is a major issue: how many additional pieces of hardware should we add?
Do we add, for example, 5 entities, and support max 5 additional VRFs? What if the customer needs only three? They paid for hardware which can service 5 VRFs and are using only 3 — not really what we would call great value for money.
What if they need more? Equally bad. Therefore, most router platform designs today implement a logical sharing of hardware resources both forwarding databases and forwarding engines.
It is important to note that all this implementation-specific stuff has some subtle consequences of importance not only to network plaform designers, but to network engineers as well: all of this can have and most often does have an impact on aspects of performance and scalability. So always, always, always bear in mind: using VRFs — as with many other features and nerd-knobs — is always an exercise in compromises.
Let me illustrate that on a single example: the total number of unicast routes a certain platform supports does not change when you implement VRFs, it is a platform limitation representing the total quantity of usually forwarding database storage available on the box.
Which consequently means that your per-VRF maximum number of routes can be limited as well. So, the first thing I wanted to know once I started messing with VRFs is — how do the new routing tables get populated?
What ends up in there now? It would be great if we could implement VRFs so that all the above still holds true, so that engineers working with virtual routing instances could have the same behavior as before, with some additions. We must instruct the router to create a new L3 entity called VRF, and provide it a hopefully meaningful name which we can use to refer to it.
When you configure a VRF, the router will in most cases [10] perform the needed partitioning of control plane and forwarding plane elements, and create the numeric ID for the VRF that we mentioned before. The static route syntax will be modified so that it is clear from the configuration in which routing table we want it to be inserted. Syntax for displaying contents of a routing or forwarding tables needs to include a reference to the VRF we want to see, ping and traceroute commands must specify in which VRF the traffic will be generated, displaying information about routing protocols running in VRFs must specify that, etc.
VRFs are a great tool for segmenting and virtualizing the network. Stay tuned! Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies.
Blog Contact Support. Request a Demo. Advantages of Virtual Routing and Forwarding The are several benefits of virtual routing and forwarding: Enables the virtual creation of multiple routes instate on one physical device Allows users to simultaneously manage multiple routing tables Can be used for MP BGP and MPLS deployments Multiple VPNs for customers can use overlapping IP addresses without conflict Users may segment network paths without multiple routers, improving network functionality VRF: Key Terms There are several key terms to define in the context of virtual routing and forwarding, and a few comparisons to make, because they answer common questions.
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