Ask the Expert: Understanding MPLS L3VPN: concepts, terminology, control and data plane call flow

[ciscomoderator]

With Vivek Ruhil

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and ask questions about MPLS L3VPN: concepts, terminology, control and data plane call flow with Cisco expert Vivek Ruhil.

MPLS Layer 3 VPNs use a peer-to-peer model that uses Border Gateway Protocol (BGP) to distribute VPN-related information. This highly scalable, peer-to-peer model allows enterprise subscribers to outsource routing information to service providers, resulting in significant cost savings and a reduction in operational complexity for enterprises. Service providers can then offer value-added services like Quality of Service (QoS) and Traffic Engineering, allowing network convergence that encompasses voice, video, and data.

Vivek Ruhil is a network consulting engineer who is currently serving as the Cisco consultant for Bharti. He has previously worked as a network consultant for planning, design, and implementation of service provider networks and has experience with projects ranging from VPNs (L3, L2, 6vPE) to multicast services. He has been associated with the networking industry for almost 10 years. He holds a bachelor of technology degree as well as CCDP and CCIP certifications.

Remember to use the rating system to let Vivek know if you have received an adequate response.

Vivek might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Service Provider sub-community discussion forum MPLS shortly after the event.

This event lasts through July 26, 2013. Visit this forum often to view responses to your questions and the questions of other community members.

[ayushmaanbhav]

Hi Vivek,

Could you please guide me to know all the steps which are needed to configure L3VPN , L2VPN and VPLS services. Also any document which can guide all the available option which can go with each command mentioned in above steps.

Thank you in advance

[Vivek Ruhil]

Hi Ayush

In order to configure a L3VPN, below are the steps:

1. Configure a VRF, you will have to set an RD(Route Distinguisher), RT(Route Target).

     ip vrf test

       rd 1:1 <<<< Unless an RD is specified, the Cisco router doesn't activate the VRF.

       route-target import 1:1 >>> You can have multiple such statements

       route-target export 1:1 >>> You can have multiple such statements

2. Attach the VRF to a customer interface

     interface Gi0/1.10

      ip vrf forwarding test

      ip address

3. Configure Routing for Customer

       router bgp

       address-family ipv4 vrf test

       neighbor statements

     In case, the customer wants to use some other routing protocol, then after the customer choosen protocol is configured redistribute that protocol in BGP

     router bgp

       address-family ipv4 vrf test

       redistribution statement

And that's it you are ready to offer L3VPN services to customers, ofcourse the infra has to be ready. Infra include, IGP, MPLS, MP-BGP.

For further information you can check the below link:

http://www.cisco.com/en/US/docs/routers/crs/software/crs_r4.1/lxvpn/configuration/guide/vc41v3.pdf

Goto "Connecting MPLS VPN Customers" Section.

For L2VPN and VPLS, since they are not part of this discussion scope I can point you to the link where the configuration for them is shared, please refer to the below link:

http://www.cisco.com/en/US/docs/ios-xml/ios/mp_l2_vpns/configuration/xe-3s/mp-l2-vpns-xe-3s-book.html

Do let me know if you need anything else.

Thanks

Vivek

[ayushmaanbhav]

Hi Vivek,

Thank you very much for your help.

Could you please also let me know the SNMP MIBs (Cisco or Standard) which can provide me the details for L3VPN, L2VPN and VPLS configured in Cisco Routers (PE and P)

If I can get any sample output, it will be great.

Regards,

Ayush

[Vivek Ruhil]

Hi Ayush

These are standard technologies deployed now a days and almost all of the NMS platforms support basic MIBs.

You can view a list of MIBs per platform from the below link:

http://www.oidview.com/mibs/9/CISCO-PRODUCTS-MIB.html

I like this one as this can give you all MIBs per IOS, per platform, per feature set:

http://tools.cisco.com/ITDIT/MIBS/MainServlet?ReleaseSel=3985&PlatformSel=45&fsSel=0

Thanks.

[jkeeffe]

In your L3VPN configuration example above, under the BGP part, you don't show any address-family vpnv4 statements.  When is it required to have an address-family vpnv4 configured under BGP?

[Vivek Ruhil]

Hi

In my reply above I pasted the steps to create a  L3vpn and stated that "ofcourse the infra has to be ready. Infra include, IGP, MPLS, MP-BGP."

To answer your next question, for L3VPN to work, below are the mandatory configurations

1. IGP (OSPF or ISIS) should be setup and working

2. MPLS

3. MP-BGP

After these basic infrastructure is ready, you can go ahead and start configuring L3 or L2 vpns.

[Vivek Ruhil]

All

I have uploaded a fairly descriptive presentation on L3VPNs which covers from  basic to advance topics

You may also go through the same and in case any questions do let me know.

https://supportforums.cisco.com/docs/DOC-34799

[ayushmaanbhav]

Hi Vivek,

Thank you for providing this presentation.

Thanks,

Ayush

[Marwan ALshawi]

Hi Vivek

I have question about MPLS-VPN and Mcast

is it now recommend and better to used mLDP instead of RSVP signaled multicast and traditional gre-MDT ?

what is the most deployed technology and what is the recommended one for IPMPLSNGN ( I believe cisco now recommending mLDP ) !!

and is it better to provision differnt VPN/VRF and link for multicast to customers or can be combined over the same vpn/VRF and link of the unicast ?

Thanks

[Vivek Ruhil]

Hi

mLDP is an interesting concept and I have personally deployed a customer network using mLDP. I would say it was practically only about selecting the right IOS . mLDP is an inbuilt function in the IOS and is straight-forward.

That being said, I would recommend that if there is a fairly new network being deployed for MVPN then we can definitely go ahead with mLDP as it brings the additional benefit that the operational staff doesn't have to be trained on another technology (PIM).

If you are already running MVPN with no problems, then I would say not to migrate unless there are problems being faced.

I couldn't understand the last question, could you please rephrase it ?

[Marwan ALshawi]

Thanks Vivek,

my last question was, if you provision MVPN to a customer and they have a unicast VPN normally as SP do you use one link to the CE or one link for mcast/mvpn and another one for unicast VPN ?

and my other question is if you are runing MVPN and wants to migrate the signaling to mLDP what is the simple way with minimum interruption that can be fallowed, e.g. I believe we can rung both without any issue get the control plan built then MP-BGP,C-Mcast and VPN can be migrate one by one ( not sure if this right approach !! )

Thanks

[Marwan ALshawi]

one more question, what is the recommend/better to be used with mLDP for mapping flow to the LSP,  BGP A-D,BGP c-mcast  or PIM

[Vivek Ruhil]

Hi

Yes you can have unicast VPN in the same VRF as Multicast VRF and it works perfectly fine.

For migration, you will have to move VPN per VPN, I mean you cannot have a customer with one VRF using mLDP and the other VRF using MVPN. One VRF within the SP has to be on either mLDP or Multicast. And yes the migration activity is done the way you have described, move one by one.

For the signalling part, IOS only uses Static mapping to mLDP flow. IOS-XR does have the options listed above but the bext one in my opinion would be using BGP A-D, cause with mLDP we are trying to move away from Multicast.

Thanks

[ayushmaanbhav]

Could you help me to get the link to understand LSP , how to configure them on Cisco Router, or with another vendor Router ?