Huawei Lab Simulations Part 4: BGP MPLS IP VPN Implementation

[@jamesmajani218]

Awesome! One question, can you please clarify the difference in functionality of MPLS inner label, outer label, RD and RT

[@LyfeyTechnologies]

Hi James, The Outer Label is the transport tunnel that is swapped by the P routers in the MPLS backbone network when the packet is moving the local PE to the remote PE. The inner label is the VPN label that helps the egress PE to identify the outgoing interface to forward the unlabeled packet. RD (Route Distinguisher) is used to make VPNv4 prefixes unique in the service provider network allowing customers to use overlapping addressing space. Route target (RT) control route import and export among PEs

[@jamesmajani218]

@@LyfeyTechnologies thanks for the clarification

[@mohaya9019]

And why don't we simply configure ebgp between PE - CE links, i mean peering under simple ipv4 family and not under vpn-instance address family

[@LyfeyTechnologies]

Hello @mohaya9019, the objective of using the VPN instances or the VRFs is to separate traffic or routing information for different customers. If we do the normal ipv4 family peering, the customer routes will be the global routing table and it will be difficult to isolate and control the routes and traffic of different customers. So we do VPN peering to CEs in the respective VPN instances. I hope this is clear enough.

[@mohaya9019]

@@LyfeyTechnologies thank-you for the prompt and clear explanation. Be blessed

[@mohaya9019]

And that is the layer 2 vpn where the SP routers are unaware of layer 3 ip info of the customer sites, right?

[@LyfeyTechnologies]

@@mohaya9019 This is L3VPN, The PE router is handling the routing information of the customer. The same information is advertised to remote PE and imported to the routing table based on the VPN target. We will have Lab simulations on L2VPN in upcoming videos.

[@LyfeyTechnologies]

@@mohaya9019 You Welcome Sir. Stay tuned in for more upcoming videos on our channel and feel free to reach out for clarifications

[@mohaya9019]

The CEs routing table shows the other site's CE loopback ip as ebgp learned route. If this is the case, then why have we used vpn? And what if we don't run import-route direct on the CEs I am confused, please shed some light to clear my confusion

[@LyfeyTechnologies]

Hello again. Thanks for watching and commenting for clarification. The Loopbacks on CEs are used to simulate network/prefixes connected to the CEs and we have advertised them to BGP. We have two options to advertise these loopbacks: 1) Using network commands on the CEs in the BGP configuration and 2) importing the direct routes. Both options can achieve the objective of having the Loopback IPs advertised to PEs via EBGP. Again, the reason of using the VPNs is to separate the routing information and the traffic from customers. We are creating multiple logical routers within one physical router. Let me know if this is clear.

[@mohaya9019]

@@LyfeyTechnologies thanks a lot. Cleared well