Hello Maheshwaran
You can achieve redundancy by placing two PE devices at one customer. How you would achieve your redundancy depends on several factors.
PE devices are typically routers, and provide you with a layer 3 operation with your on site equipment. In other words, the PEs will act as a default gateway for your customer networks. If this is the case, then the most common solution is to use BGP at the customer edge between your CEs and PEs and perform multi homing. That way, your redundancy is achieved via the BGP routing protocol. Alternatively, you can use an IGP like OSPF or EIGRP to load balance all of your traffic towards the service provider across the PEs. So in such a scenario, you are configuring redundancy using Layer 3 (routing).
Now in the diagrams you shared, you are suggesting using multi chassis LAG, that is, a portchannel (EtherChannel) to connect to PE routers. This is not ideal, because of several reasons:
- PE devices are typically routers (Layer 3) and they are provided by the ISP. Although some router platforms do support it, Etherchannel is primarily a technology deployed on switches.
- Secondly, even if you have PE routers that do support it, you would have to arrange with the ISP to have them set up their end appropriately, and it must be within the parameters that they are willing to deliver for you.
- If you were to create a port channel as shown in your first diagram, you wouldn’t have an active and backup PE, nor would you run iBGP between them or any type of FHRP such as HSRP or VRRP. You would have to use some high availability option for routers such as VSS or vPC (for nexus switches only). These are not good solutions for a PE device that’s part of an ISP.
Now the portchannel option in your second diagram is more feasible because you are eliminating the need for the ISP’s PE router to support MC-LAG, but you are asking the PE to deliver a Layer 2 connection to your premises. That has to be done in coordination with your ISP, but it’s doable.
Keep in mind that EtherChannel, MC-LAG, FHRPs such as VRRP and HSRP etc are all technologies that are typically used within an enterprise network, and often within datacenters. They are not often deployed at the network edge. The preferrable solutions for the redundancy you’re looking for is Layer 3 routing enabling redundancy via multiple paths. That way the PE routers can remain independent and less coordination is necessary with the ISP.
Ultimately, I believe that the most often used solution for such redundancy would be layer 3 redundancy
I hope this has been helpful!
Laz