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Mario Rosi

PWHE for a L2VPN and L3VPN, a hierarchical approach without SDN




as you can see from the sketch, i've a MPLS Segment Routing core backbone (made of ASR9K as S_PE) and different islands instead composed of NCS540 as A_PE. The services that will be transported are the classic for an ISP, L2VPN and L3VPN.

Since the number of A_PE would be quite huge (they could reach the number of almost on thousand per single island) i decided to split the ISIS domain in L2 for the core and L1 for the islands (S_PE so will be working as L1/L2 edge router).

I don't need to introduce L2 into L1 leaking because, i just need the mgnt subnet to be reached by A_PE and vice versa, the A_PE's Lo again for the mgnt.

For the rest i would like to implement a hierarchical solution but without requiring the insertion of PCE (no Unified MPLS) and NSO, to make easier the whole solution.

So, finally my idea would be:

- L2VPN service: A_PE implement only BGP EVPN among them and with S_PE so that: PW VPWS EVPN can be set up among themselves for intra Domain L1 L2VPN service and L2 PWHE interface can be set on S_PE for inter Domain end2end L2VPN service

- L3VPN service: A_PE again, thanks to BGP EVPN set up also L3 PWHE interface on S_PE that end on a VRF and from there the L3VPN service is released by S_PE with BGP L3VPN among themselves

Now, my questions are:

1) For the L3VPN service, ok, it's quite clear, a PWHE ending on a VRF on S_PE and that's it, but for the L2VPN service, which would be the configuration on S_PE in order for them to collect L2 PWHE interfaces bound with L2 A_PEs' tunnels and at the same time tunnel them using BGP EVPN on the L2 ISIS core? i.e.: A_PE sets a L2 PWHE towards S_PE, S_PE take that L2 PWHE interface and xConnect with BGP EVPN configured on L2 core backbone to transport the L2 frames over the remote S_PE and again towards remote A_PE with another L2 PWHE... i don't find any configuration that shows me how it can be done

2) May i set a L2/L3 PWHE interface on S_PE that collect all the VLANs relatives to the clients connected to the same A_PE (so, only one PWHE tunnel per A_PE towards S_PE) and then spill the single L2/L3 sub-PWHE interface on S_PE?

If you have any suggestions, examples, docs i would be very grateful because i didn't find anything.

Best regards,