Routing to 2 gateways on the same subnet (Migration to new WAN provider)

[HmksInc67088]

Hi all - I am switching to a new provider for MPLS between my corporate office and remote sites.  The subnets at each site are pretty standard (172.16.<site#>.0) with the corporate/hub site being 172.16.1.0).  Currently traffic inside the corporate LAN has a route to use the provider router (172.16.1.1) to get to the remote site subnets (172.16.2.0, 172.16.3.0 etc).  Each site has between 80 - 90 devices already active so it will be extremely impractical to change the IP schema.  I need to be able to switch the sites over one at a time to a new provider.  If I have my existing provider router in place and have the NEW provider router have an IP of 172.16.1.101 can I attach it to the same outside switch and change the static route per remote network and roll the sites over one by one and just swap the WAN connection at the remote sites to the new provider device?

I'm using C1111-8P with UNIVERSALK9_IAS at all sites.

I've included the details in a simple drawing attached to this post as well.

[balaji.bandi]

Technically possible - as long as you have  arrangement with MPLS provider is important.

what kind of MPLS - Layer 2 ? do you run any VPN / or IGP ?

you can start with 1 Site and test how it goes, by learning lessons you can move to other site as per the process learned first cutover.

(make sure on the 1st site, keep ready your test plan to test all related to business before you move to other site)

[HmksInc67088]

Its only layer 2 no vpn or igp so hopefully it will work fine - i should be able to test it today when the hub site device is put in.

[balaji.bandi]

sure test and advise - you should be ok ?

[Richard Burts]

The approach that you suggest where the new provider router gets an address in that subnet, and where you have static routes to reach each remote site, and could change the static routes, one at a time, to move sites from old provider to new provider should work ok.

[Giuseppe Larosa]

Hello @HmksInc67088 ,

I suppose you have an MPLS L3 VPN service and you are moving to a new provider using the same type of service L3 VPN.

I have one note:

traffic between remote sites happen via the central site only or remote sites are allowed to communicate between them directly?

Because in the second case the migration is more difficult when you move the test site under the new provider the other sites are not able to reach it unless going to the central site.

If direct traffic between remote sites is not allowed  (VPN hub and spokes with Central services) your migration plan is fine.

Other considerations would apply if you have a VPLS L2 service for inter site connectivity.

Hope to help

Giuseppe