VPN Label in MPLS VPN L3

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hi bro ,

in very brief , normally VPN label distribution when using MPLS along with what known with VPN-instance ( VRF ) , the PE device will assign this label to the routes revived from the CE before advertising them to other PE through MB-BGP .

the PE can assign those labels through two different way :
1- separate label for each route received from the CE .
2- one label per instance , means all the routes received on specific VPN-instance ( VRF ) regardless of how many routes .

kindly go through the documents for further and advance information .

To carry customer private routes or native IP packets through MP-BGP network, PE device adds a label in the NLRI field for each data packet.

PE has to select a VPN instance for data forwarding to CE. To ensure proper transmission, another label is added to identify the VPN instance to which each packet belongs.
Therefore, packets have two labels one is IGP label is on the top (outer label), and a VPN label is at the bottom (inner label). IGP labels are distributed by LDP or RSVP to all Ps and PEs hop by hop. VPN labels are advertised by MP-BGP between PEs.

Here is more information to follow

https://support.huawei.com/enterprise/en/doc/EDOC1000178321/b5f87131/bgp-mpls-ip-vpn-fundamentals

https://forum.huawei.com/enterprise/en/mpls-vpn-data-forwarding-plane/thread/553757-863

Hi hamza11,

A VPN label is a unique label allocated by a PE to each VPN route. The remote PE advertises the VPN label to the local PE through BGP. As shown in the following figure, after PE1 receives the VPN label advertised by PE2 to its VPN1, PE1 adds the VPN label of VPN1 when accessing CE2.

I hope it helps!

Hi hamza11, 

When CE1 accesses CE2, CE1 sends an IP packet to PE1. After receiving the packet, PE1 adds the VPN label VPN1 to the packet based on the VPN label advertised by PE2, searches the forwarding table, and adds the outer MPLS label MPLS-1 to the packet based on the next hop, send the packet to the P device. After receiving the packet, the P removes the outer MPLS-1 label, adds the outer MPLS-2 label to the packet based on the next hop in the forwarding table, and sends the packet to PE2. After receiving the packet, PE2 removes the outer MPLS-2 label and VPN label VPN1 from the packet and sends the IP packet to CE2.

Thank u for the information