What is VRF?

[exhilaratedsri]

Hi

please explain me what is VRF also I have found that vrf can be configured on both router and switch. I have 3750 and 3800 so where should I configure vrf.

[Leo Laohoo]

VRF goes hand-in-hand with MPLS.  Start reading here.  

[exhilaratedsri]

Thanks for quick response Leo. I looked at the config guide, I found VRF config is done on routers

but then I found about vrf lite

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/31sg/configuration/guide/vrf.pdf

The config is done on switches here. Can you explain me the difference and impact.

[Marwan ALshawi · Accepted solution]

VRFs in general used to virtualizes the routing tables where you can have multiple routing tables in one physical router

VRFs can be used with MP-BGP and MPLS for network like ISPs

also VRFs can be used locally to perform separation between multiple routing instances aka VRF lite

both can be used for Path isolation

useful links

http://packetlife.net/blog/2010/mar/29/inter-vrf-routing-vrf-lite/

http://www.cisco.com/en/US/docs/solutions/Enterprise/Network_Virtualization/PathIsol.html

hope this help

plz rate the helpful posts

[Joseph W. Doherty · Accepted solution]

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Posting

VRF is sort of the L3 version of VLANs.  Whether it should be configured on your 3750 or 3800 or both depends on your needs.

To your later question about the "lite" version of VRF, this often doesn't support as many VRF instances and, on low-end devices, uses VLAN tags or GRE tags to support multiple VRF instances between devices where the full blown version uses MPLS tags.  (NB: When multiple devices share multiple VRFs across a single link, they need some way to distinguish what VRF a packet belongs to.  Sort of the L3 version of a L2 trunk.)