2 years ago

EVPN – Ethernet VPN, has been quite popular in the IT industry since it was invented. Many companies deployed it for various reasons. It was initially invented to solve some problems for MPLS-based Layer 2 VPNs, but over time, not only Layer 2 VPNs but also supported Layer 3 VPNs as well. Although initially, it started for MPLS and PBB – Provider Backbone Bridging data plane, VXLAN as a data plane gained so much more popularity and today, most of the EVPN deployments use VXLAN for the data plane. Thus, in this short post, we will look at why EVPN is the next generation VPLS, but for more info about it, check this EVPN VXLAN Advantages Course definitely.

EVPN allows multipathing in the Core Networks

VPLS as a Layer 2 VPN cannot provide multipath in the core network. This means, that when there is traffic destined to the remote sites, let’s say customer network, behind two PE devices, only one of those PE devices can be used to send the traffic. Another can be backup.

EVPN can allow Multipathing in the Core networks, so the resources can be used efficiently and in case of link or node failure, only half of the traffic can be affected until the network converge again.

EVPN allows Active-Active Flow-based Load Balancing

Active-Active Flow-based means, connecting the CE devices to the two PE devices and sending the different flows over different links, even those flows are in the same VLAN.

Let’s explain this a little bit more for clarification.

CE device can be connected to two 2 or more PE devices.

In this case, we call this type of connection dual-home or multi-home.

When the CE device is connected to more than one PE device, with classically Spanning Tree, VPLS, or any other Layer 2-based solution, only one of the links from CE to PE can be active for 1 VLAN.

If you have two VLANS, let’s say Vlan 10 and Vlan 20, Vlan 10 can be active on one link, and Vlan 20 can be active on another link.

This means all the flows of VLAN 10 can be mapped to one link only, and all the flows of VLAN 20 can be mapped to another link.

Obviously, there can be thousands, if not millions of flows in even medium-sized networks.

So, sending different flow traffic over different links can provide granular traffic engineering/manipulation.

EVPN can provide sending different flows, even if they are in the same VLAN, over different links, without creating any Layer 2 loops.

This gives EVPN more granularity.

Some flows might have more traffic than others and the Network administrator can carry different flows over the different links with EVPN without causing any loops. On the website of OrhanErgun, there are many posts that are covering Layer 2 and Layer 3 loops, Vlan and Flow-based details, Network Convergence and Traffic Engineering with Layer 2, IGP, BGP, and MPLS. If you are interested in Network Engineer, you will check it for more blog posts.

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