what is vrf

[mahesh.dasari]

Can any one explain me how VRF works

recently i am configuring a 4500 e series switch iam no able to ping the switch from my laptop.But iam able to ping it from other switches can any one tell me why

the command i found on the switch is IP VRF MGNT-VRF

[John Blakley]

VRF stands for virtual routing and forwarding. When you create a vrf, you tell it what routes to import/export. Then you assign that vrf to an interface. Once the vrf is attached to an interface, the switch/router creates a separate routing table to hold those routes. To see those, you'd type "sho ip route vrf MGNT-VRF".

VRF are used in MPLS and VRF-Lite implementations. So a vrf would look like this:

ip vrf MGNT-VRF

rd 100:100

rt export 100:100

rt import 100:100

ip vrf Red

rd 200:200

rd both 200:200 (export and import)

Under the interface:

int g0/1

ip vrf forwarding Red

ip address 192.168.200.1 255.255.255.0

int g0/2

ip vrf forwarding MGNT-VRF

ip address 192.168.100.1 255.255.255.0

Any global address that you have on your switch will still be in what's now called the "global routing table" and any addresses assigned to the above 2 customers are in their respective VRF.

HTH,

John

[Peter Paluch]

John,

I guess that what you wanted to say but isn't clear is that the VRF is a separate routing table within a router. VRFs are to a router what VLANs are to a switch. Using VRFs, it is possible to virtualize a single router into several instances, each of them being (relatively) independent of each other, allowing for overlapping subnets, separate instances of routing protocols, separate set of interfaces assigned to each VRF, etc.

Best regards,

Peter

[John Blakley]

"Once the vrf is attached to an interface, the switch/router creates a separate routing table to hold those routes."

I thought I said that here...

Either way, the OP stated that it wasn't working while pinging to the switch from a connected host, but can from another switch. Chances are the vrf that the user is in isn't importing the route that the vrf MGNT-VRF is exporting OR the user isn't in a vrf and the management address is which would then need to leak the address in the global routing table. Correct?

[Bahaa J]

from cisco guide 

[viplove]

It is Virtual Route forwarding, we use when we need a different routing table on the same device.
With this you can use same bunch of IP address and routing that you are using on default vrf, to segregate the customers using same IP. 

There are many uses of vrf that you can find on cisco docs. Go through them.