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New Member

VPN label

Hi There,

can anybody throw some light on how vpn labels assigned and exchanged between PE routers for vrf subnets since P routers only knows about global subnets?

Regards,

Rajesh

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: VPN label

Rajesh,

The VPN labels are exchanged between PE via the mBGP VPNv4 updates. As you indicated, the P routers are completely oblivious of these updates, unless of course a P router is used as a route reflector, in which case it will obviously need to hold the VPNv4 prefixes (control plane only).

The MPLS packet switching from the ingress to the egress PE is performed based solely on the outside label also known as IGP label.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
4 REPLIES
Cisco Employee

Re: VPN label

Rajesh,

The VPN labels are exchanged between PE via the mBGP VPNv4 updates. As you indicated, the P routers are completely oblivious of these updates, unless of course a P router is used as a route reflector, in which case it will obviously need to hold the VPNv4 prefixes (control plane only).

The MPLS packet switching from the ingress to the egress PE is performed based solely on the outside label also known as IGP label.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: VPN label

can u have any diagram which clearly shows how mpls vpn label are exchanged. I dont have any problem if u can provide me hand made diagram also

Cisco Employee

Re: VPN label

Sumit,

Here are a couple of slides that might help.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: VPN label

Hi,dude

vpnv4 lables only knows at PE routers and these exchanged with other PEs by MP-BGP.

P router don't know about these vpnv4 lables. So in common MPLS VPN environment, PE router assign 2 lable to packet so called vpnv4 lable & vpn lable. only P router lookup outermost lable and switch packet to another PE.

Once another PE received lable it look up vpnv4 label and switch the packet to correct VRF.

HTH

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