How to Aggregate two MPLS Ethernet Circuits

[Brian Aeschliman]

Currently our plants are connected via a single MPLS circuit. We need to increase bandwidth and increase reliability for our plant connections. I am looking to understand if I can aggregate two MPLS (fiber ethernet) links, so I can take advantage of the extra bandwidth, as well build in redundancy so that a local fiber cut won't take both legs down. I am hoping someone in this forum can answer if it is possible, and if so identify what I would need to do to accomplish this objective.

Summarize:

Today's Setup: Single MPLS to each plant setup as Primary Connection, and the Internet circuit is used only as a IPsec backup path.

Proposal: To have two MPLS circuits provided by the same carrier, but have them engineered so that they have diverse paths connected to different CO's, and diverse last mile carriers, so that any fiber cuts won't down both circuits. Then to keep the IPsec as a third backup path if needed.

[Richard Burts]

Perhaps if we knew more about your environment we might be able to give better advice. But based on what we know so far I have these comments which I hope may be helpful:

1) when we talk about aggregating Ethernet one option frequently is to configure EtherChannel. This takes multiple physical connections and uses them in a single logical connection which provides increased bandwidth and redundancy in the case of loss of a physical connection. But I do not think that is possible when you are dealing with MPLS.

2) With MPLS you could treat two Ethernet as two layer 3 connections, run a routing protocol over both connections which could provide some load sharing/increased bandwidth as well as providing redundancy in the case of loss of one Ethernet. But some people would say that this is not aggregating. So how strict is your definition of aggregating?

HTH

Rick

[Brian Aeschliman]

Rick,

We are looking for something more inline with your option 2. Externally over the MPLS we use BGP, and internally we generally don't implement a routing protocol past the core switch. Our LAN is structured as a collapsed core. When we do deploy internal routing protocols generally we use OSPF and then inject those routes into the external BGP. The other difficulty is our environment is a divestiture, so the IP schema at each site is a bit of a mixed bag, so things like route summarization is not generally available, we use static routing for most of our internal L3 routing requirements. If you have any specific questions about our environment, please send them my way and I will do my best to answer them

As for the load balancing question, I don't have any specific requirements, other than saying we want the most efficient use of the aggregated bandwidth. 

Thanks,

Brian

[Richard Burts · Accepted solution]

Brian

I am not clear what you are telling us when you describe your network as  divestiture. But it may not be important. For the purpose of answering the question in your original post we will focus on the BGP used to route between sites. I am assuming that when you add the second MPLS that it will be to the same provider but to a different provider router/different provider site. You would run BGP on both MPLS connections and receive BGP route advertisements on both connections. I am also assuming that the provider is advertising the full set of routes from all the sites rather than advertising just a default route. In this case it is possible that some remote sites may be more attractive on one connection than on the other connection and you would achieve load balancing. If the  remote sites are all equally attractive then you might configure an inbound route map on each BGP neighbor to make some sites preferable using the first connection and other sites more preferable using the second connection by setting local preference or weight on certain remote routes learned from each neighbor. If the provider is advertising only a default route then you would need to set up some Policy Based Routing to send outbound traffic to some sites using the first connection and to send traffic to other sites using the second connection. 

What I have described will provide load sharing for traffic that you send outbound. To provide load sharing on traffic that you receive you might want to configure an outbound route map for each neighbor. In the route maps you would advertise all of your internal prefixes to each neighbor and you would use prepending on some prefixes for connection one and prepending of other prefixes on connection two so that the provider will route some traffic preferring connection one and other traffic using connection two.

HTH

Rick 

[Richard Burts]

Brian

You asked an interesting question. I am glad that my suggestions have been helpful. Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information.

HTH

Rick