Suggestions; changing enterprise ISP + current MPLS routing

Question

My company currently has MPLS and DIA coming from one provider. The firewall allowing all the sites connected to break out onto the DIA is hosted in the MPLS cloud. Now we are upgrading our DIA, but will be using a different ISP. We will keep the MPLS network intact but we are moving the DIA off the MPLS into the Head Office itself.

Picture attached to make things a bit clearer. So what I am trying to show here is that remote sites previously routed through the MPLS firewall but now all traffic should be routed to the head office routers which then break out.

What I want is for all traffic to remain routed the same for now but want to be able to test the new routing schematic. It was suggested that another VLAN be created on the MPLS routers which all points to the head office router and then that router points to the new firewall. I am not certain that default gateways can be set per-vlan? I would think a whole vrf would be necessary?

So the question really is; is there a way I can test the new routes while maintaining current connectivity?

Answer 1

It is never possible to test a routing change until it has been implemented so the direct answer to your direct question is "no".

But that's not really helpful. More generally, consider why you want to test it and what you really mean by that.

Normally a business wants to test that a new service works. And then wants post-implementation testing to gain confidence that the new service works for all users in the final state or in several intermediate states, with a roll-back plan if it doesn't.

So you can test the DIA service with isolated Internet clients at the head office or using client-specific rules on a proxy or whatever is suitable for your particular configuration.

You can then make whatever change you have planned, and ensure that you have a plan to test that change, and a plan to roll-back wiothion a defined window if necessary. Note that if your current ISP actually makes that routing change, then you will need to make sure the roll-back plan includes the ISP and is agreed by the ISP. It may be possible to devise an implementation method that does not involve the ISP directly during your change window.

Note that implementation may have to be big-bang for all your sites (unless you want to start tinkering with different vrfs), but that doesn't mean that all Intenet destinations have to be rolled over at the same time, some key routes might be retained on the old DIA initially.

Ultimately it's about business risk and you need to manage it appropriately. If there's not much risk then you don't need much testing.