MPLS Service decision

[dolrairom]

Hello everyone! I'm studying advanced networks architecture for college and the I have the following doubt:

Supposing a scenario where a client is present in 3 different cities, the client wants that all the trafic between city 1 and 2 goes first to city 3 (as a head office), which would be the better mpls service?
What I see is the need of a point to point connection from city 1 to 3 and another one from city 2 to 3. My main thought is that the network would be based on L2VPN (VPWS), and not VPLS because in this one, the PE choose the AC depending on the destination MAC, so city 1 and 2 could get direct communication. But, why not L3VPN? I can't get to the decision. I read the post https://community.cisco.com/t5/mpls/difference-between-l2vpn-and-l3-vpn/td-p/2986112 and still can't make up my mind.

Please I need some help, thanks!

[Francesco Molino]

Hi

How are your sites connected together today? I believe they are running ip services (routing) and not connected over L2 links?
You can do the exact same thing using L3VPN in multiple ways (segment routing, traffic-engineering...).
Do you have a need to stretch L2? what kind of services are you planning to run?
If you can summarize it briefly, L3VPN will consider each site as a real site with routing in between (even if you can L2 afterwards if needed) whereas L2VPN will be 3 physical locations in 1 big logical location as your L2 will be spanned (maybe not all vlans..). This is a schematic view to make you decide which one to go with and most importantly depending on what services you need to run.

[Giuseppe Larosa]

Hello @dolrairom ,

as noted by Francesco a connectivity model with city3 site Central Hub can be implemented also with MPLS L3 VPN by using different route targets on spoke sites city1 and city2 that will import a default route from the central site.

It is a special form of Hub and Spokes topology implemented with different route targets.

As already noted to take a decision on what type of service to use you need to understand the user needs at the diffferent sites.

If you don't need to extend any Vlan between sites the MPLS L3 VPN with the described tricks can be a viable option.

Hope to help

Giuseppe

[dolrairom]

Hello @Francesco Molino and @Giuseppe Larosa , thanks for your replies.
The client itself is an adsl provider with head office in city 3, which wants to see all the traffic between its two clients on cities 1 and 2 (sorry for not telling this in the first post, I thought it was irrelevant). So there is no need for vlans, the provider just wants to reroute their clients traffic. So as @Giuseppe Larosa commented, no vlans are need so the best service would be L3VPN, wouldn't it?

Thanks,

Dolrairom.

[Giuseppe Larosa]

Hello @dolrairom ,

if your traffic is IP traffic you can use an MPLS L3 VPN service with Hub and Spokes and Central services.

Your understanding is correct.

Hope to help

Giuseppe

[Francesco Molino]

@Giuseppe Larosa  already replied.

You're right no vlan needed in your MPLS cloud, much easier and avoid playing with L2 spanned on all sites. However, if you have the need in the future for any reasons, your MPLS cloud is already built and will help you doing that.

For traffic engineering, it will be a lot easier with MPLS L3 VPN cloud.