WAN design (dual WAN providers, MPLS, BGP multi-homing)

The customer is wanting to convert to a new WAN architecture that will provide a dual/redundant carrier architecture.

Specifically, they currently have a single MPLS carrier between all of their locations, each site having two circuits into the carrier cloud (single MPLS VLAN, not dual/separate). As they route via BGP to the carrier, each site has a single BGP ASN. The WAN routers perform re-distribution so they do not currently run iBGP between the two carrier CE routers.

The newly proposed architecture is to have a single circuit from the current carrier and another from a new carrier into each site, with each circuit terminated on individual/separate routers. To ensure session load balancing, bandwidth utilization, cost routing, etc., they're hoping for consulting experience/expertise to provide design input.

Stated options/questions include:

- whether to run iBGP between WAN routers and what impact the AS numbering may have
- the most effective (yet simplest) way to run performance routing code, etc that they need to understand how best to run the new WAN architecture
- cutover/migration plans/advice

So, we're looking for examples from similar designs - dual MPLS clouds with divergent carriers and how to design around problems.
Very broad, I know, but any/all input that can be provided would be appreciated.  As always, reference links/docs are appreciated.
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cfan73Author Commented:
We settled on running iBGP between the dual perimeter routers at each location, each ISR connected to a single MPLS carrier. Extended communities will be used to tag priority data at ingress and provide QoS at egress. Local preference will be used to force the voice traffic over a particular carrier w/ failover to the other.

We just needed to get everyone in the room and hash it out. BGP only at the edge, OSPF within each location, no redistribution required.
If you have enough MTU available, you may want to consider running GRE tunnels between CE routers, across the MPLS VPN clouds - and then run your IGP (OSPF?) inside the GRE tunnels. Then the design is simpler, and you may not even need BGP even to the provider.

In general BGP is a very nice protocol, since there is a lot of manual control, but effectively it means you need to do most things manually, based on the network in questions. For example, load-balancing will mean setting higher local preference for the networks you want to send via a specific MPLS provider - and then translate that to an IGP metric.

I would also consider getting a L2VPN or VPLS service instead, and connect that directly to CE routers - and run the IGP across the VPN.
cfan73Author Commented:
Thanks for your feedback - will consider, but keeping this thread open for additional input (hopefully addressing the original requirements along with your suggestions).
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If you are using OSPF then another option is to use OSPF sham links across the VPN.
cfan73Author Commented:
I've requested that this question be closed as follows:

Accepted answer: 0 points for cfan73's comment #a38445956

for the following reason:

Internal team developed the recommended solution
You may have chosen a different design, for what ever internal reasons, but there is nothing wrong with the options I provided.

I find it rather cheap not assigning the points.
cfan73Author Commented:
Internal team developed the recommended solution -

I certainly wasn't trying to be "cheap" in accepting my own answer, so not sure about that comment. What I wasn't aware of was the ability to accept your own answer yet still award points to others for valuable input.  I've corrected that here, awarded points, and will follow this process moving forward.

Thanks, all.
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