Amazon VPC Site-To-Site tuning / filtering

Hi everyone,

We have two sites running UTMs that have an OSPF connection to each other over private link. They also have AWS VPC site-to-sites to the same VPC instance.

     AWS VPC

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Office 1 -    Office 2

Is there a best practice advised for how to set these up? There isn't much control in the GUI, and I'm finding each other's office site routes being learnt via AWS because BGP trumps OSPF. There seems to be not much documentation that I could find in the way of design guides or anything close to it that describes this.

I could make the  inter-site link  BGP which would fix as both the AS_PATH would be less, and it also turns out that any BGP route learned via AWS is set to WEIGHT 0. I don't want to  go down this path because the convergent times are too low and I frankly shouldn't have to.

I can't do any route filtering on the UTM because its just a GUI and all that is hidden from you. I don't dare touch the bgpd.conf files because of the support threat of making you rebuild the UTM if things don't work.

I was thinking of just making each site's AS number the same for the VPCs so that BGP loop avoidance doesn't install the route but it seems to be a hack way of doing something that should be straight forward.

Any ideas good citizens?

Matt