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If you are using Microsoft Peering, that means a certain Public IPV4 Range "Advertised public prefixes" is validated by Microsoft.
Certain IPs would be advertised from your OnPrem into Microsoft.
- Only then, Microsoft would send the traffic destined to the OnPrem Public IPs via the ExpressRoute.
- Else, no Traffic flows inside the Microsoft Peering.
- I am not exactly sure what you mean by "default gateways" as I am not sure about the router side configuration.
- From each the /30 subnet you specify, the first usable IP address is assigned to your router and Microsoft uses the second usable IP for its router.
- The "Advertised public prefixes" uses this IP to route into Microsoft Routing domain and Microsoft services send the traffic destined to this "Advertised public prefixes" via the Microsoft Peering.
- Refer : Microsoft peering
Your statement says that you are not "advertise default or Intranet routes".
- However, for Microsoft peering to work , you should advertise some Public IP prefixes you own as stated above.
- There are two /30 subnets, one for each Primary Connection and Secondary Connection.
- If you advertise a lengthier AS path for secondary connection, Microsoft will prefer the primary connection (shorter AS Path).
Please let us know if we can be of any further assistance here.
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