Hello Everyone,
Today, I will discuss about the Ethernet Virtual Private Network EVPN also known as an all-in-one VPN solution for the next generation. EVPN was developed by the Internet Engineering Task Force (IETF) and published in 2014 in the RFC 7209. If we look back at the history of this, we can see that there has been a lot of changing have taken place so far. As shown in figure 1.
Figure 1 VXLAN finally comes of the age with EVPN
IETF was intended to introduce EVPN in order to overcome the limitations of traditional L2VPN with providing innovative features and better improvement over the existing layer 2 architecture in an agile manner.
Figure 2 Tradional L2VPN vs EVPN
The Advantagies of EVPN
There are a number of significant benefits to using EVPN, which are listed below.
EVPN is open standards-based architecture in order to support backwards and forwards interoperability.
EVPN provides all-active multi-homed network topology, network segmentation inside, and across multiple campuses and data centers.
EVPN improves the efficient integration of Layer 2 and Layer 3 connectivity with control plane-based learning.
EVPN is preventing loops in layer 2 network and eliminates the need to broadcast ARP requests.
EVPN allows flexibility, easy network scalability based on business needs.
EVPN improves network reliability by reducing protocols complexity.
Ethernet VPN is technology that connects layer 2 network segments separated by a layer 3 network, and EVPN enable to connect dispersed customer site using a layer 2 virtual Bridge EVPN accomplishes this by building the layer to network as a virtual layer to overlay layer 3 network uses BGP as its control protocol. let's discuss about different devices role in EVPN or Ethernet VPN comprises of CE, PE and P devices.
[CE Customer Edge]. CE is the customer edge devices as normally router or layer 2 switch the provide access to PE device.
[PE Provider Edge]. PE is the provider edge router connects to the customer site and maintain EVPN and its specific information. PE or provider edge device form the edge of MPLS infrastructure. PE device provides layer 2 virtual bridge connectivity between the CE devices.
[P Provider]. P is provider router do not carry EVPN instead they simply provide label switching router services to facilitate the transfer of label frame between PE routers.
Ethernet VPN Terminologies
let’s discuss about different Ethernet VPN terminologies.
The first type of terminology is Ethernet VPN instance or also known as EVI. Ethernet VPN instance is an EVI routing and forwarding instance spanning all the PE routers participating in that VPN or you can say it is defined as all the P divides participating in the specific EVPN. EVI is configured on the PE router on per customer basis and each EVI has a unique route distinguisher and one or more route-target.
The second type of terminology is the Ethernet Segment that typically described as ES. When customer site is connected to one or more PEs via set of ethernet links. That set of ethernet link is called as ethernet segment, ethernet segment appears on the link aggregation group lack to the CE device. The link from router PE-1 to PE-3 device to CE-1 for many ethernet segment. As shown in figure 3.
Figure 3 EVPN networking
There is another type of terminology we have is Ethernet Segment Identifier and it is called ESI. Multi-homed CEs which is active-active or active-standby required unique ESI for the links. PEs need to used same unique ESI when connected to the same CE device. Single home CE devices do not require any ESI as by default attend the result value.
The last we will discuss about EVPN operation. EVPN uses MP-BGP mechanism and is the main signaling protocol used by EVPN. Ethernet VPN provide the way to learn and distribute MAC addresses cross customer sites by using MP-BGP. Hence MAC address learning happens at the control plane, EVPN defined new sub-address family and EVPN address family in the L2VPN address family. In the EVPN address family a new type of NLRI is added that is EVPN NLRI. It defines several types of BGP EVPN routes which can carry information such as the host IP address, MAC address and etc.
EVPN advertise five route types using MP-BGP.
Type 1 route Ethernet A-D or auto discovery route.
Type 2 route MAC/IP advertisement route
Type 3 route inclusive multicast route
Type 4 route Ethernet segment route
Type 5 route IP-prefix router advertisement
Conclusion
The fundamental concept of this post is to overview of EVPN and also identify the new features and benefits bring with EVPN for the network operators. I hope that this post will be helpful to network engineers when they will implement EVPN in their operational network.
Thank you!
References
https://support.huawei.com/enterprise/en/doc/EDOC1100168670
https://info.support.huawei.com/info-finder/encyclopedia/en/EVPN.html
https://www.juniper.net/us/en/research-topics/what-is-evpn-vxlan.html
https://datatracker.ietf.org/doc/html/rfc7432
https://datatracker.ietf.org/doc/html/rfc7209
https://techfieldday.com/
