Need help on VRF lite

ganpatspatil · ‎05-08-2007

I have implement VRF lite feature for one of the customer...it's working fine..But i m not so clear of following command ...........Can any one explane the same.

router ospf 511 vrf abc

capability vrf-lite <--------What is use of this command..is this is reletaed to BGP to OSPF redistribution..?

mohammedmahmoud · ‎05-09-2007

Hi,

VRF lite converts the router into multiple virtual routers each one with its separated routing table, interfaces and routing protocols.

The OSPF Support for Multi-VRF on CE Routers feature provides the capability of suppressing provider edge (PE) checks that are needed to prevent loops when the PE is performing a mutual redistribution of packets between the OSPF and BGP protocols. When VPN routing and forward (VRF) is used on a router that is not a PE (that is, one that is not running BGP), the checks can be turned off to allow for correct population of the VRF routing table with routes to IP prefixes.

When the OSPF process is associated with the VRF, several checks are performed when link-state advertisements (LSAs) are received. PE checks are needed to prevent loops when the PE is performing a mutual redistribution between OSPF and BGP interfaces. In some situations, performing PE checks might not be desirable. The concept of VRFs can be used on a router that is not a PE router (that is, a router that is not running BGP). With the capability vrf-lite command, the checks can be turned off to allow correct population of the VRF routing table with routes to IP prefixes.

This command suppresses the Provider Edge (PE) specific checks on a router when the OSPF process is associated with the VRF.

HTH, please do rate all helpful posts,

Mohammed Mahmoud.

mounir.mohamed · ‎05-09-2007

Dear ganpatspatil,

OSPF multi-VRF allows you to split the router into multiple virtual routers, where each router contains its own set of interfaces, routing table, and forwarding table.

This command "capability vrf-lite " Applies the multi-VRF capability to the OSPF process.

For more details, kindly check the below URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122s/122snwft/release/122s14/ospfvrfl.htm

Please rate helpful posts.

Best Regards,

Mounir Mohamed

ganpatspatil · ‎05-09-2007

Thanks For Reply Mohamed ......

When PE redistribute route from BGP to OSPF it will set Down Bit to avoid loops....

you want to say.....

In VRF lite When PE set down bit to route

and when this route come to CE in perticular VRF is that down bit cleared

Is it ?If yes than how loop will avoided.

mohammedmahmoud · ‎05-09-2007

Hi,

The whole idea is to disable the checks (which is a must on the PE doing redistribution) in order not to introduce any problems when populating the VRF table on a multi-VRF CE router running OSPF.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

ganpatspatil · ‎05-09-2007

Then how loop will be avoided ?

mohammedmahmoud · ‎05-09-2007

Hi,

On a CE router running multi-VRF you won't need this technique to avoid routing loop (if you are doing redistribution), while its a must on a PE router talking BGP with other PE routers and each PE router is talking OSPF to its CE routers and each PE router is doing redistribution.

When VPN routing and forward (VRF) is used on a router that is not a PE (that is, one that is not running BGP), the checks can be turned off to allow for correct population of the VRF routing table with routes to IP prefixes.

Again the whole idea of this command is to disable the checks (which is a must on the PE doing redistribution in an MPLS backbone) in order not to introduce any problems when populating the VRF table on a multi-VRF CE router running OSPF.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.